Because the RNAi experiments potentially eliminate all isoforms of Cbs and the antibody does not distinguish between the three, it was of interest to know the effects of the loss of GRIP-domain function on embryogenesis and Cbs behavior. It is known that the GTPase Arl1 interacts directly with the GRIP domains in the yeast Imh1p, human Golgin-245 and human Golgin-97 proteins, and is required for GRIP function (Hickson, 2003; Lu, 2003; Lu, 2004; Panic, 2003a; Panic, 2003b; Setty, 2003; Van Valkenburgh, 2001; Wu, 2004). To gain insight into the function of the Cbs GRIP isoform, Cbs and Centrosomin (Cnn) were examined in an Arf72A-mutant background during early embryogenesis, using the Arf72A1-mutant allele of the Drosophila Arl1-encoding ortholog. Arf72A1 is a recessive lethal allele, and mutant embryos fail at cellularization and early gastrulation (Eisman, 2006).
The mitotic localization pattern of Cbs is dramatically changed in an Arf72A1-mutant background. During early prophase, Cbs changes from a haze to larger particles, similar to wild type, but particles do not concentrate around nuclei and the density of Cbs shows considerable variation across the embryo. Cbs particles persist in the cytoplasm throughout mitosis, occasionally forming large aggregates, but fail to localize with DNA from metaphase to telophase. These particles fail to completely fragment during telophase and appear to be degraded as development proceeds. Centrosome maturation proceeds normally in most embryos through the early syncytial blastoderm stage, but a low percentage of centrosomes are either small or fused. During the late syncytial blastoderm stage, the number of centrosome and nuclear fusions increases, and the total amount of Cbs present decreases significantly (Eisman, 2006).
Throughout late preblastoderm and syncytial blastoderm cycles the FI levels of Cbs are relatively constant and variation between nuclei remains high during all stages of mitosis. Although Cbs particles appear to be uniformly scattered throughout the embryo during these stages, Cnn FI values vary from approximately double normal levels to nearly zero and Cnn immunostaining is highly variable among nuclei, in contrast to wild-type embryos (Eisman, 2006).
During cellularization Cbs intensity is significantly less than wild type in Arf72A1 embryos and Cbs fails to concentrate in the pericentriolar region, remaining as a haze above the apical surface of nuclei. Additionally, Cbs is absent at the lateral surface of nuclei, and centrosomes vary in size between members of a pair and from cell to cell; however, they are larger than those found in RNAi embryos. In addition to loss of most Cbs, Lva FI values are 80%-85% lower in these embryos, and many nuclei drop away from the cortex, similar to the RNAi cellularization phenotype. Unlike the RNAi embryos, the alignment of the remaining nuclei at the cortex of Arf72A1 mutant embryos is almost normal, suggesting that centrosomes are partially functional, and that the loss of Lva and failure to cellularize is directly due to the loss of Arl1 function (Eisman, 2006).
Approximately 63% of the embryos complete cellularization and initiate gastrulation prior to failure, but furrow- and segment-formation is weak or incomplete, giving the cortex a smooth, flat appearance. Mitotic domains have fewer cells than in wild type and many spindles have a single centrosome. In general, the density of nuclei is low in these embryos, many nuclei appear to be aneuploid, and both Cbs and Lva are significantly reduced or absent in most cells (Eisman, 2006).
The Arf72A mutant data shows that Arl1 is necessary for the transport of Cbs from the cytoplasm to the chromosomes, and that this process is required to maintain Cbs and Lva protein levels during syncytial development. The initial formation of Cbs particles during early prophase is normal, suggesting that this process involves one or both of the non-GRIP isoforms of Cbs. Additionally, because the transport of Cbs to the chromosomes appears to be microtubule-dependent, this suggests that Arl1 and the GRIP domain are required for localizing Cbs to microtubules. Although the loss of Arl1 function most probably affects other proteins, the fact that localization of Cnn to centrosomes is aberrant, and Lva is lost in both RNAi depletion and Arf72A-mutant embryos, suggests that the interaction between Arl1 and the GRIP domain is conserved in Drosophila, and Cbs is a target of Arf72A (Eisman, 2006).
To characterize the wild-type pattern of Cbs accumulation during early embryogenesis, Cbs was coimmunostained for with various combinations of antibodies against: Cnn, a core component of the centrosome, Lava Lamp (Lva), a cis-Golgi protein required during cellularization and microtubules (α-tubulin), as well as for DNA and PDI::GFP, a fusion protein that marks the ER (Bobinnec, 2003). Cbs was followed throughout mitosis during four stages of embryogenesis: preblastoderm (cycles 1-9), syncytial blastoderm (cycles 10-13), cellularization, and early gastrulation. In addition to the pattern of Cbs described below, there is a pool of Cbs particles at the embryonic cortex that becomes gradually depleted during syncytial development (Eisman, 2006).
During the early preblastoderm divisions (cycles 1-7), Cbs is difficult to detect in the cytoplasm at prophase. However, by prometaphase Cbs is localized to chromatin, where it remains until early telophase. At this point Cbs appears to fragment into small particles and is undetectable by the completion of mitosis. The association of Cbs with chromosomes from metaphase throughout anaphase is characteristic of all four stages of development studied (Eisman, 2006).
During late preblastoderm and syncytial blastoderm stages, the prophase and telophase pattern of Cbs becomes more complex. As chromosomes begin to condense during early prophase Cbs particles begin to form in a haze around nuclei. During late prophase, cytoplasmic Cbs staining becomes more particulate and Cbs begins to accumulate within the nuclei during early chromosome congression. As spindles elongate during prometaphase Cbs is localized to the spindles and chromosomes, and is present only at chromosomes by late metaphase, maintaining this association until late anaphase B. By late telophase, as mid-bodies begin to break down, Cbs staining appears to fragment into smaller particles. These Cbs particles appear to completely break down by the completion of telophase, again forming a dense cytoplasmic haze around nuclei (Eisman, 2006).
The association of Golgi proteins with chromosomes during mitosis has not been reported in Drosophila, suggesting that preparative conditions may be important for their detection. The fixation method used has been optimized for the preservation of syncytial microtubule structures, so two different formaldehyde preparations were tested, with and without a Taxol pre-treatment, to preserve microtubules. Under these latter conditions, in the absence of Taxol, the early prophase pattern of Cbs is the same, but the association of Cbs with chromosomes is barely detectable or even absent. However, when embryos were treated with Taxol prior to formaldehyde fixation Cbs association with chromosomes is readily detectable from metaphase to early telophase, although immunostaining intensity is lower than what was observed with the initial preparative method. Thus, it appears that microtubule stability is required for the detection of Cbs on chromosomes, whereas the early prophase changes in the localization of Cbs from the cytoplasm to the nucleus is less sensitive to the preservation of microtubules. The differential detection of Cbs during these two stages of Cbs reorganization during mitosis suggests that there are two different mechanisms required for these processes (Eisman, 2006).
To quantify Cbs and Cnn immunostaining during these stages of development the relative fluorescence intensity of protein around nuclei was analyzed at different stages of mitosis. Fluorescent intensity (FI) of Cbs is highest during prophase, with considerable variation between individual nuclei. The FI and variation decreases approximately 50% during metaphase and begins to increase during anaphase B and telophase. The only significant differences in FI values during cycles 8-13 are 30% reductions in Cbs intensity during cycle 13 prophase and during cycle 12 and 13 metaphase. The FI values for Cnn remain relatively constant in wild-type embryos, with minimal variation among nuclei, throughout mitosis during syncytial development (Eisman, 2006).
During the cellularization stage, as nuclei enter the first prolonged interphase in Drosophila development, centrosomes replicate and move 2-4 µm apart along the apical surface of nuclei, where they remain throughout cellularization of the blastoderm. The accumulation pattern of Cbs displays two separate components during this stage of development. Immediately after centrosome replication, Cbs particles form a concentrated region of staining that fills the gap between the centrosomes and extends partway into the region between the centrosomes and nucleus. During formation of this region of Cbs concentration, weak colocalization with Cnn was detected within replicated centrosomes. As cellularization continues, Cbs staining is also present as a cytoplasmic haze surrounding the entire lateral surface of each columnar nucleus, and there is a fourfold increase in the Cbs FI level. As is the case for Cbs association with the mitotic chromosomes, the outer portion of the Cbs pericentriolar concentrated region and the lateral domain appears to be microtubule-dependent because it is best preserved with the same preparative methods. The concentrated pericentriolar region and cytoplasmic haze of Cbs staining persists throughout most of cellularization, but recedes to just the pericentriolar region prior to cytokinesis (Eisman, 2006).
During gastrulation, the pattern of Cbs in mitotic domains is the same as that described for late syncytial nuclear cycles. In interphase cells during very early gastrulation, and in cells along segments and embryonic furrows, Cbs forms a dense perinuclear structure and a cytoplasmic haze that is closely apposed to the nuclei. However, by late gastrulation and throughout the rest of embryogenesis, most interphase cells have multiple Cbs foci of variable size that are surrounded by a weak cytoplasmic haze (Eisman, 2006).
In general, the amount of detectable cytoplasmic Cbs during late telophase and early prophase increases between the preblastoderm and syncytial blastoderm nuclear cycles. During all stages of development, Cbs FI cycles from high levels at prophase to reduced levels during metaphase and anaphase when Cbs is associated with chromosomes. The association of Cbs with chromosomes during mitosis and the later expansion of Cbs during cellularization appear to be microtubule-dependent. Throughout cellularization and early gastrulation, Cbs remains concentrated between centrosomes on the apical surface of nuclei. This region of Cbs fragments and disperses throughout the cytoplasm during late gastrulation. A persistent cytoplasmic pool of Cbs was also observed throughout mitosis during syncytial blastoderm cycles, which is undetectable at mitosis during the preblastoderm divisions (Eisman, 2006).
All known GRIP domain proteins are found at the trans Golgi, and are implicated in vesicle tethering and transport, strongly supporting a role for Cbs at the trans Golgi in Drosophila. Of the known Drosophila Golgi proteins, Lava Lamp (Lva) seemed a likely candidate to interact with Cbs. Lva is a golgin-like Golgi protein that interacts with actin, microtubles, CLIP190, Spectrin complexes and the cis-Golgi protein p120. It is also required for dynein-dependent membrane vesicle transport from the Golgi to the growing furrow front during cellularization. Although the localization of Lva is complex during cellularization, a fraction of Lva maintains a pericentriolar location throughout the process, similar to the pericentriolar Cbs staining described above (Eisman, 2006).
During the preblastoderm and syncytial blastoderm stages, in addition to the cytoplasmic pool of Lva, it was found that Lva colocalizes with chromosome-associated Cbs transiently during early chromosome congression. This association is no longer detectable by the time chromosomes are tightly aligned along the metaphase plate. Additionally, this colocalization was observed only when microtubules were rapidly fixed or stabilized with Taxol prior to formaldehyde fixation, and the FI is strongest in rapidly fixed embryos (Eisman, 2006).
At the start of cellularization strong colocalization between Cbs and Lva was detected at the pericentriolar region of spherical nuclei, and this association persists throughout most of cellularization. As cellularization continues, a second population of Lva vesicles that is basal to the nuclei moves to the pericentriolar region by a microtubule-dependent mechanism, concomitant with the formation of the cytoplasmic haze of Cbs along the lateral surface of nuclei described above. Throughout this process Lva FI levels increase in a similar manner to Cbs, although Lva intensity is significantly less than Cbs. Small puncta of Cbs and Lva colocalization are present throughout this lateral domain but the larger, basal and apical Lva particles were not observed in this region. Cbs and Lva do not colocalize at growing membrane furrows above nuclei, and the only Cbs present above the pericentriolar region are scattered cortical particles (Eisman, 2006).
On the basis of the previously described dynamic behavior of Lva during cellularization, the known interactions between Lva and other cis-Golgi proteins, and the strong colocalization with Cbs at the pericentriolar region, it is proposed that Lva moves from the cis Golgi to the trans Golgi where it associates with Cbs before it is transported to the growing-furrow fronts. Additionally, Cbs and Lva colocalize transiently during chromosome congression prior to formation of a compact metaphase plate, which may be important for Golgi maintenance (Eisman, 2006).
The relationship between the ER and the Golgi complex during mitosis is a key issue in the debate over the mechanism of Golgi inheritance in animal cells. A transgenic fly line that expresses PDI::GFP under control of the endogenous PDI promoter was used to mark the ER lumen throughout the cell cycle (Bobinnec, 2003) and to determine whether Cbs is present within the ER lumen during mitosis. It is important to note that the immunostaining pattern for PDI::GFP in embryos fixed with the initial preparative method is similar to the published live pattern for this ER marker (Eisman, 2006).
During syncytial blastoderm and cellular stages, the ER and Cbs are present together throughout the cytoplasm during early prophase, but there is no evidence for colocalization of the two proteins. The ER begins to condense around nuclei during late prophase, concomitant with the movement of Cbs from the cytoplasm to the interior of the nuclei. Throughout metaphase and anaphase, the ER forms an envelope around the mitotic spindle, but is excluded from the spindle proper and the regions of Cbs localization. ER dispersal to the cytoplasm begins during early telophase, and the ER is prophase-like by the time Cbs fragmentation begins at late telophase (Eisman, 2006).
During cellularization and early gastrulation, the ER accumulates above the centrosomes, and weak colocalization is detected between ER projections and the closely apposed pericentriolar Cbs region. This is consistent with EM data from rat kidney cells, where it has been proposed that the direct transfer of lipids from the trans ER to the trans Golgi, rather than the typical transport through the Golgi, provides a rapid mechanism to generate new plasma membrane (Eisman, 2006).
From these data and the original report on the PDI::GFP marker (Bobinnec, 2003) it is concluded that, Cbs is not present in the lumen of the ER throughout mitosis in Drosophila and is actively inherited by daughter cells via a mechanism independent of the ER (Eisman, 2006).
The effect of the loss of Cbs has on early embryogenesis was determined to ascertain the cellular function of Cbs. Because of the lack of any known mutations in Cbs, the Gal4/UAS-inducible expression system was used to target all possible cbs transcripts for RNA interference (RNAi)-induced degradation by using the Symp-UAST RNAi vector. Additionally, flies were raised at different temperatures to regulate GAL4-induced transcription. The majority of embryos produced by females raised at 18°C develop normally and there is no apparent sterility in the nanos----->cbs (a GFP::GRIP fusion protein during embryogenesis under control of nanos::Gal4) females. Approximately 25% of the embryos produced by females that were kept at 25°C and 83% of the embryos produced by females that were kept at 29°C had severe defects. Despite these differences, a similar range of protein depletion that varies from a moderate depletion to an apparent complete loss of Cbs is seen in embryos, as evidenced by significantly reduced fluorescent intensity (FI) values at 25°C and 29°C. A fraction of embryos fail during syncytial blastoderm and cellularization stages at both temperatures, but the frequency of failure is much higher in embryos produced by females raised at 29°C. None of the temperatures investigated caused any obvious defects during the preblastoderm stage of embryogenesis. The phenotypes described below were not observed in control embryos (Eisman, 2006).
During syncytial blastoderm stages, the severity of the defects in embryos correlates with the amount of reduction in FI levels for Cbs. Moderate phenotypes are present in embryos with at least half the wild-type FI levels of Cbs, and severe defects are associated with significant reductions in FI levels. During prophase, moderate reductions in Cbs results in centrosomes that vary in size, and Cnn staining is less compact than that observed in wild-type centrosomes. Additionally, there frequently are acentrosomal nuclei present. In more severely depleted embryos, cytoplasmic Cbs-particle formation is barely detectable during prophase, Cnn staining at centrosomes is reduced, the frequency of acentrosomal nuclei increases and the nuclei appear to be degraded. During metaphase moderate depletion of Cbs results in aberrant spindle formation, which varies from short, broad spindles, to completely collapsed spindles. Aberrant spindles usually have asymmetric centrosomes based on Cnn staining, even when the detectable amount of Cbs at metaphase chromosomes appears to be normal. In syncytial blastoderm embryos that have no detectable Cbs staining, metaphase spindles typically have a single centrosome with Cnn staining, most likely due to defective spindle attachment, and these embryos probably die. In all the embryos with a significant reduction in the FI levels of Cbs, the FI levels of Cnn are also significantly reduced as compared with wild-type embryos (Eisman, 2006).
If Cbs is significantly depleted at the start of cellularization, the pericentriolar Cbs staining is diminished or absent and centrosome maturation is impaired for 20-50% of the nuclei. The level of Cnn in one centrosome of a pair is often barely detectable, and frequently only one centrosome is competent to nucleate astral microtubules, consistent with an earlier finding that Cnn is required for the mitotic localization of γ-tubulin to the centrosome and the formation of astral microtubules. As cellularization proceeds, the pericentriolar Cbs-concentrated region remains small, Cbs fails to localize to the lateral region around nuclei and Lva staining is absent. Lateral sections through these embryos show that nuclei are poorly aligned at the cortex and many drop from the cortex, which might be due to the combined loss of Cbs and functional centrosomes. Based on the morphology of these embryos, it is unlikely that they complete development (Eisman, 2006).
In most embryos that complete cellularization, gastrulation appears to be normal and cells seem to have wild-type levels of Cbs. The gross morphology of these embryos is only mildly affected and many of them can potentially complete development. The post-cellularization phenotypes may improve because the effect of maternal RNAi is negligible by this stage of development and zygotic gene expression could allow cells to recover (Eisman, 2006).
On the basis of these RNAi results, it is concluded that a significant pool of maternally loaded cbs transcript is necessary to perpetuate the normal cycling of Cbs during mitosis. The Cbs cycle is necessary for maintaining centrosome number and morphology, and for maintaining sufficient levels of Lva. Although significantly lower than wild-type levels of Cbs appear to be sufficient for development to proceed, when Cbs levels fall below a minimum value development fails. During syncytial development failure is due to centrosome defects, whereas failure at cellularization is minimally due to the combined loss of Cbs, Lva and defective centrosomes. It is concluded that normal cycling and sufficient protein levels of Cbs are required during all stages of development following cortical migration in Drosophila (Eisman, 2006).
The GRIP domain has been shown to be a trans-Golgi localization signal in eukaryotes, and overexpression of this domain interferes with the function of endogenous GRIP proteins in a concentration-dependent manner. Based on the Arf72A-mutant data, ectopic expression of the GRIP domain during embryogenesis should interfere with Cbs transport during mitosis, causing cellularization and centrosome defects. To test the Cbs GRIP function in Drosophila during embryogenesis, a 45-amino-acid fragment that aligned with the Golgin-97 GRIP sequence at different temperatures was expressed to obtain a range of phenotypic responses to low and high levels of GFP::GRIP expression (Eisman, 2006).
The localization of the GFP::GRIP fusion protein during syncytial cycles is very similar to endogenous Cbs, although the early prophase cytoplasmic haze for the fusion peptide is weaker. During the early stages of centrosome replication, GFP::GRIP localizes to both centrosomes, but is significantly more concentrated at one centrosome. In 37% of the embryos assayed at 25°C, excess Cnn was observe at prophase centrosomes, based on immunostaining and FI values, leading to centrosome hypertrophy and asymmetric centrosome pairs (Eisman, 2006).
In an additional 15%-28% of the embryos assayed, centrosome hypertrophy is associated with re-replication of individual centrosomes. Up to seven centrosomes were observed associated with a single nucleus, and enlarged centrosomes are frequently found that appear to be in the process of separating again. Whenever centrosome hypertrophy is severe, there are free cytoplasmic centrosomes and an increase in the number of nuclei that are acentrosomal or contain a single centrosome, suggesting that the fusion peptide also interferes with centrosome attachment to the early spindle during prophase (Eisman, 2006).
During metaphase and anaphase the GRIP domain localizes strongly to centrosomes and spindle microtubules, but is nearly absent from chromatin. Interestingly, high concentrations of the GRIP domain at metaphase and anaphase centrosomes do not lead to precocious replication, because replicating centrosomes are never seen during these stages of mitosis (Eisman, 2006).
The GRIP domain also interferes with the transport of native Cbs protein, because there is a significant increase in the number of cytoplasmic Cbs particles during metaphase, which are not present at this stage in wild-type embryos. Additionally, the FI values for Cbs at nuclei and spindles are lower during prophase and metaphase, suggesting that the GFP::GRIP domain interferes with proper localization of Cbs (Eisman, 2006).
If centrosome hypertrophy is severe, embryos fail because of mitotic defects (including multipolar spindles and severe aneuploidy) prior to cellularization. However, presumably due to the inherent variability of the GAL4 system, less severely affected animals are seen, and these embryos could potentially complete cellularization and embryogenesis. Consistent with this possibility is the fact that even at 29°C nanos---->GFP::GRIP mothers can produce viable progeny. Interestingly, in the defect-free animals the fusion protein does not persist in cellularized embryos, implying that the maternal supply of GFP::GRIP is degraded at this point in development (Eisman, 2006).
From these findings and the Arf72A mutant data, it is concluded that the GRIP domain is required for the transport of Cbs from the cytoplasm to the chromosomes, but that it is not the primary motif for chromosome or microtubule attachment. Additionally, the GFP::GRIP fusion peptide colocalizes with Cnn at the center of the centrosomes throughout mitosis, and interferes with the normal localization and function of Cnn. This association may be an exaggeration of the weak colocalization between Cnn and Cbs at centrosomes during early cellularization. Although the mechanism that links Cbs and Cnn transport to the centrosome remains unclear, it appears that, by blocking the efficient transit of Cbs to the chromosomes due to excess GFP::GRIP protein at centrosomes during prophase, the centrosome cycle can be uncoupled from the cell cycle (Eisman, 2006).
Reference names in red indicate recommended papers.
Search PubMed for articles about Drosophila Cbs
Alzhanova, D. and Hruby, D. E. (2006). A trans-Golgi network resident protein, golgin-97, accumulates in viral factories and incorporates into virions during poxvirus infection. J. Virol. 80(23): 11520-7 81(3): 1539. Medline abstract: 16987983
Alzhanova, D. and Hruby, D. E. (2007). A host cell membrane protein, golgin-97, is essential for poxvirus morphogenesis. Virology [Epub ahead of print]. Medline abstract: 17276477
Barr, F. A. (1999). A novel Rab6-interacting domain defines a family of Golgi-targeted coiled-coil proteins. Curr. Biol. 9: 381-384. Medline abstract: 10209123
Barr, F. A. and Short, B. (2003). Golgins in the structure and dynamics of the Golgi apparatus. Curr. Opin. Cell Biol. 15: 405-413. Medline abstract: 12892780
Behnia, R., Panic, B., Whyte, J. R. and Munro, S. (2004). Targeting of the Arf-like GTPase Arl3p to the Golgi requires N-terminal acetylation and the membrane protein Sys1p. Nat. Cell Biol. 6: 405-413. Medline abstract: 15077113
Bobinnec, Y., Marcaillou, C., Morin, X. and Debec, A. (2003). Dynamics of the endoplasmic reticulum during early development of Drosophila melanogaster. Cell Motil. Cytoskeleton 54: 217-225. Medline abstract: 12589680
Dirac-Svejstrup, A. B., Shorter, J., Waters, M. G. and Warren, G. (2000). Phosphorylation of the vesicle-tethering protein p115 by a casein kinase II-like enzyme is required for Golgi reassembly from isolated mitotic fragments. J. Cell Biol. 150: 475-488. Medline abstract: 10931861
Eisman, R. C., Stewart, N., Miller, D. and Kaufman, T. C. (2006). centrosomin's beautiful sister (cbs) encodes a GRIP-domain protein that marks Golgi inheritance and functions in the centrosome cycle in Drosophila. J. Cell Sci. 119(Pt 16): 3399-412. Medline abstract: 16882688
Frescas, D., Mavrakis, M., Lorenz, H., Delotto, R. and Lippincott-Schwartz, J. (2006). The secretory membrane system in the Drosophila syncytial blastoderm embryo exists as functionally compartmentalized units around individual nuclei. J. Cell Biol. 173: 219-230. Medline abstract: 16636144
Gilson, P. R., Vergara, C. E., Kjer-Nielsen, L., Teasdale, R. D., Bacic, A. and Gleeson, P. A. (2004). Identification of a Golgi-localised GRIP domain protein from Arabidopsis thaliana. Planta 219: 1050-1056. Medline abstract: 15605178
Hickson, G. R., Matheson, J., Riggs, B., Maier, V. H., Fielding, A. B., Prekeris, R.,Sullivan, W., Barr, F. A. and Gould, G. W. (2003). Arfophilins are dual Arf/Rab 11 binding proteins that regulate recycling endosome distribution and are related to Drosophila nuclear fallout. Mol. Biol. Cell 14: 2908-2920. Medline abstract: 12857874
Jesch, S. A., Mehta, A. J., Velliste, M., Murphy, R. F. and Linstedt, A. D. (2001). Mitotic Golgi is in a dynamic equilibrium between clustered and free vesicles independent of the ER. Traffic 2: 873-884. Medline abstract: 11737825
Jokitalo, E., Cabrera-Poch, N., Warren, G. and Shima, D. T. (2001). Golgi clusters and vesicles mediate mitotic inheritance independently of the endoplasmic reticulum. J. Cell Biol. 154: 317-330. Medline abstract: 11470821
Kjer-Nielsen, L., Teasdale, R. D., van Vliet, C. and Gleeson, P. A. (1999). A novel Golgi-localisation domain shared by a class of coiled-coil peripheral membrane proteins. Curr. Biol. 9: 385-388. Medline abstract: 10209125
Lock, J. G., et al. (2005). E-cadherin transport from the trans-Golgi network in tubulovesicular carriers is selectively regulated by golgin-97. Traffic 6(12): 1142-56. Medline abstract: 16262725
Lu, L. and Hong, W. (2003). Interaction of Arl1-GTP with GRIP domains recruits autoantigens Golgin-97 and Golgin-245/p230 onto the Golgi. Mol. Biol. Cell 14, 3767-3781. Medline abstract: 12972563
Lu, L., Tai, G. and Hong, W. (2004). Autoantigen Golgin-97, an effector of Arl1 GTPase, participates in traffic from the endosome to the trans-golgi network. Mol. Biol. Cell 15: 4426-4443. Medline abstract: 15269279
Lu, L., Tai, G., Wu, M., Song, H. and Hong, W. (2006). Multilayer interactions determine the Golgi localization of GRIP golgins. Traffic 7(10): 1399-407. Medline abstract: 16899086
Luke, M. R., Kjer-Nielsen, L., Brown, D. L., Stow, J. L. and Gleeson, P. A. (2003). GRIP domain-mediated targeting of two new coiled-coil proteins, GCC88 and GCC185, to subcompartments of the trans-Golgi network. J. Biol. Chem. 278: 4216-4226. Medline abstract: 12446665
Luke, M. R., Houghton, F., Perugini, M. A. and Gleeson, P. A. (2005). The trans-Golgi network GRIP-domain proteins form alpha-helical homodimers. Biochem. J. 388: 835-841. Medline abstract: 15654769
McConville, M. J., Ilgoutz, S. C., Teasdale, R. D., Foth, B. J., Matthews, A., Mullin,K. A. and Gleeson, P. A. (2002). Targeting of the GRIP domain to the trans-Golgi network is conserved from protists to animals. Eur. J. Cell Biol. 81: 485-495. Medline abstract: 12416725
Panic, B., Perisic, O., Veprintsev, D. B., Williams, R. L. and Munro, S. (2003a). Structural basis for Arl1-dependent targeting of homodimeric GRIP domains to the Golgi apparatus. Mol. Cell 12: 863-874. Medline abstract: 14580338
Panic, B., Whyte, J. R. and Munro, S. (2003b). The ARF-like GTPases Arl1p and Arl3p act in a pathway that interacts with vesicle-tethering factors at the Golgi apparatus. Curr. Biol. 13: 405-410. Medline abstract: 12620189
Pelletier, L., Jokitalo, E. and Warren, G. (2000). The effect of Golgi depletion on exocytic transport. Nat. Cell Biol. 2: 840-846. Medline abstract: 11056540
Preisinger, C. and Barr, F. A. (2001). Signaling pathways regulating Golgi structure and function. Sci. STKE 2001PE38. Medline abstract: 11687710
Seemann, J., Jokitalo, E., Pypaert, M. and Warren, G. (2000). Matrix proteins can generate the higher order architecture of the Golgi apparatus. Nature 407: 1022-1026. Medline abstract: 11069184
Seemann, J., Pypaert, M., Taguchi, T., Malsam, J. and Warren, G. (2002). Partitioning of the matrix fraction of the Golgi apparatus during mitosis in animal cells. Science 295: 848-851. Medline abstract: 11823640
Setty, S. R., Shin, M. E., Yoshino, A., Marks, M. S. and Burd, C. G. (2003). Golgi recruitment of GRIP domain proteins by Arf-like GTPase 1 is regulated by Arf-like GTPase 3. Curr. Biol. 13: 401-404. Medline abstract: 12620188
Shima, D. T., Haldar, K., Pepperkok, R., Watson, R. and Warren, G. (1997). Partitioning of the Golgi apparatus during mitosis in living HeLa cells. J. Cell Biol. 137: 1211-1228. Medline abstract: 9182657
Shima, D. T., Cabrera-Poch, N., Pepperkok, R. and Warren, G. (1998). An ordered inheritance strategy for the Golgi apparatus: visualization of mitotic disassembly reveals a role for the mitotic spindle. J. Cell Biol. 141: 955-966. Medline abstract: 9585414
Sutterlin, C., Hsu, P., Mallabiabarrena, A. and Malhotra, V. (2002). Fragmentation and dispersal of the pericentriolar Golgi complex is required for entry into mitosis in mammalian cells. Cell 109: 359-369. Medline abstract: 12015985
Takatsuki, A., Nakamura, M. and Kono, Y. (2002). Possible implication of Golgi-nucleating function for the centrosome. Biochem. Biophys. Res. Commun. 291: 494-500. Medline abstract: 11855815
Tamkun, J. W., Kahn, R. A., Kissinger, M., Brizuela, B. J., Rulka, C., Scott, M. P. and Kennison, J. A. (1991). The arflike gene encodes an essential GTP-binding protein in Drosophila. Proc. Natl. Acad. Sci. USA 88: 3120-3124. Medline abstract: 1901655
Van Valkenburgh, H., Shern, J. F., Sharer, J. D., Zhu, X. and Kahn, R. A. (2001). ADP-ribosylation factors (ARFs) and ARF-like 1 (ARL1) have both specific and shared effectors: characterizing ARL1-binding proteins. J. Biol. Chem. 276: 22826-22837. Medline abstract: 11303027
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date revised: 5 March 2007
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