disc proliferation abnormal
See the embryonic expression pattern of dpa at the Berkeley Drosophila Genome Project Patterns of Gene Expression Site.
The high levels of transcript in 0-3 hour embryos indicate a maternally supplied message. Expression levels increase in 3-6 h embryos and reach a maximum level at 6-9 hours. The transcript level is reduced by 9-12h and only very low levels are detected after 12 hours (Feger, 1995).
The expression pattern of dpa is dynamic during gastrulation and germband extension. Most tissues express the transcript at high levels but some areas have very little or no expression. The epidermal expression remains high until late stage 11, when it is extinguished. Expression is then found in the delaminated neuroblasts of the CNS and the sensory organ precursors of the PNS. The dividing sensory organ precursors of the PNS continue to express the gene until stage 13/14 when expression ceases, concomitantly with the end of cell division. Most or all cells in the ventral nerve cord and brain show high transcript levels from stages 10 through 12, whereas only a subset of CNS cells express the transcript from stages 13 onwards. The gene is also expressed in endoreplicating tissues, starting in the anterior and posterior midgut at stage 12 followed by hindgut expression at stage 13 and, shortly afterwards, expression in the Malpighian tubules (Feger, 1995).
Expression of dpa is detected in cells of the third instar larvae in eye imaginal disc cells ahead of the morphogenetic furrow, and in a tight band behind it, but not in the furrow itself, coinciding with the first and second mitotic waves of proliferating cells. In the CNS of third instar larvae, expression is evident in the mitotically active optic lobes and in those neuroblasts that produce ganglion mother cells (Feger, 1995).
Minichromosome maintenance (MCM) proteins are essential eukaryotic DNA replication factors. The
binding of MCMs to chromatin oscillates in conjunction with progress through the mitotic cell cycle.
This oscillation is thought to play an important role in coupling DNA replication to mitosis and limiting
chromosome duplication to once per cell cycle. The coupling of DNA replication to mitosis is absent in
Drosophila endoreplication cycles (endocycles), during which discrete rounds of chromosome
duplication occur without intervening mitoses. The behavior of MCM proteins was examined in
endoreplicating larval salivary glands, to determine whether oscillation of MCM-chromosome
localization occurs in conjunction with passage through an endocycle S phase. MCMs in
polytene nuclei exist in two states: either associated with or dissociated from chromosomes. DmMCM2, DmMCM4, and DmMCM5 are detected as nuclear proteins in polytene nuclei of salivary glands during the three larval instars. In a majority of polytene nuclei from second- and third- instar larvae (>80%), most of the nuclear MCM stain is excluded from the region occupied by DNA and the nucleolus. It is inferred that most of the nuclear MCMs are not asociated with chromosomes in these nuclei and this pattern is referred to as nucleoplasmic. In contrast, in a small fraction of nuclei (~10%), nuclear MCM staining is coincident with the DNA. This state is interpreted as indicating a chromosomal association of MCMs. Cyclin E is expressed in transient pulses, each of which overlaps the beginning of each endocycle S phase. cyclin E mutants fail to undergo endoreplication. Heat induction of cyclin E produces a synchronous burst of DNA synthesis in polytene cells lasting between 3 and 6 hours. 40% of nuclei display chromosomal DmMCM2 after heat shock, and this association rapidly diminishes. Thus heat induction of Cyclin E drives chromosome association of DmMCM2. Subsequently, DNA synthesis erases this
association. To test whether DNA synthesis is required for the dissociation of DmMCM2, DNA synthesis was blocked with an inhibitor, aphidicolin. In the presence of aphidicolin, chromosome-associated DmMCM2 is retained for up to 3 hours after induction of S phase by cyclin E, apparently stabilizing the association of DmMCM2 with chromosomes. It is concluded that DNA replication is required for dissociation of DmMCM2 from chromosomes. Thus, mitosis is not required for oscillations in chromosome binding of MCMs
and it is proposed that cycles of MCM-chromosome association normally occur in endocycles. These results demonstrate that the cycle of MCM-chromosome associations is uncoupled from
mitosis because of the distinctive program of cyclin expression in endocycles (Su, 1998).
There is maternal expression of dpa throughout oogenesis. The transcript accumulates in late oogenesis in the nurse cells before it is transferred to the oocyte (Feger, 1995).
Homozygous mutant animals develop into third instar larvae of normal size but pupariation is slightly delayed. Mutant animals die during pupal development. No imaginal discs are found in larval animals and the CNS of mutant larvae is reduced in size. Presence of endoreplicating tissues such as the gut, fat body and polytene chromosomes suggests that dpa is required during mitotic but not during endoreplicating cell cycles. Disc primordia are normal, as revealed by an escargot mRNA hybridization probe and antibodies specific for the Snail protein (Feger, 1995).
More cells are labeled with BrdU in stage 16 embryos than are normally found. Despite the ectopic labeling, mutant larvae show fewer ganglion mother cells surrounding putative neuroblasts. This suggests that the cell cycle is prolonged in mutant flies, and that dpa function is required for the regulation of DNA replication in neuroblasts (Feger, 1995).
Chorion gene amplification in the ovaries of Drosophila is a powerful system for the study of metazoan DNA replication in vivo. Using a combination of high-resolution confocal and deconvolution microscopy and quantitative realtime PCR, it was found that initiation and elongation occur during separate developmental stages, thus permitting analysis of these two phases of replication in vivo. Bromodeoxyuridine, origin recognition complex, and the elongation factors minichromosome maintenance proteins (MCM)2-7 and proliferating cell nuclear antigen were precisely localized, and the DNA copy number along the third chromosome chorion amplicon was quantified during multiple developmental stages. These studies revealed that initiation takes place during stages 10B and 11 of egg chamber development, whereas only elongation of existing replication forks occurs during egg chamber stages 12 and 13. The ability to distinguish initiation from elongation makes this an outstanding model to decipher the roles of various replication factors during metazoan DNA replication. This system was used to demonstrate that the pre-replication complex component, Double-parked protein/Cdt1, is not only necessary for proper MCM2-7 localization, but, unexpectedly, is present during elongation (Claycomb, 2002).
Three independent lines of evidence are presented that initiation and the bulk of elongation at a chorion amplicon occur during two separate developmental periods. (1) Deconvolution microscopy shows that ORC and BrdU initially colocalize at origins and then diverge, since ORC is lost in stage 11 and BrdU resolves into a double bar structure. (2) Elongation factors PCNA and MCM2-7 follow the same pattern as BrdU, resolving from foci early in amplification to a double bar structure by stage 12 to 13. (3) Quantitative realtime PCR shows a peak increase in DNA copy number at the origins by stage 11, with increases in flanking sequences becoming substantial in stages 12 and 13. Thus initiation ends by stage 11, and during stages 12 and 13 only the existing forks progress outward. Furthermore, these observations led to the unanticipated conclusion that DUP/Cdt1 travels with replication forks (Claycomb, 2002).
The realtime PCR and immunofluorescence data are remarkably consistent. (1) Both methods restrict initiation to stages 10B and 11 of oogenesis, and elongation to stages 12 and 13. Between stages 10B and 11, the maximum fold amplification was detected at amplification control element (ACE) on third chromosome (ACE3) by realtime PCR, ORC localized to origins, and the deconvolution showed a maximum increase in bar length. During stages 12 and 13, increases in fold amplification were detected only proximal and distal to ACE3, and ORC no longer localized to origins, whereas BrdU incorporation resolved into the double bar structure. (2) The distances of fork movement are consistent. Deconvolution measurements predicted that forks were maximally 30 +/- 3 kb apart in stage 10B, and this correlates with the 40-kb span of peak copy number detected by realtime PCR. In stage 11, forks were measured to have progressed across a 55 +/- 13-kb region by deconvolution and across a 45-kb region by realtime PCR. By stage 13, deconvolution showed that replication forks were maximally separated by 74 +/- 7 kb, whereas realtime PCR measured a 75-kb span (Claycomb, 2002).
The quantitative analysis of the amplification gradient provides insight into mechanisms affecting fork movement and termination and suggests that an onionskin structure impedes fork movement. The maximal rate of fork movement during amplification has been calculated to be 90 bp/min on average. In comparison, replication forks in the polytene larval salivary glands travel at ~300 bp/min (Steinemann, 1981), whereas rates of fork movement in both diploid Drosophila cell culture and embryo syncytial divisions are ~2.6 kb/min. From these rates, it seems that polyteny hinders replication fork movement, an effect even more pronounced in amplification, given that the chorion cluster has a rate of fork movement three times less than polytene salivary glands. The fact that by stage 13 there is a gradient of copy number, and not a plateau, further demonstrates the inefficiency of fork movement along the chorion cluster (Claycomb, 2002).
There do not seem to be specific termination sites to stop forks either along or
at the ends of the chorion region, but fork movement may display some sequence or chromatin preference. The gradient of decreasing copy number implies that forks stop at a range of sites, because the presence of specific termination points along the region would be expected to cause steep drops in copy number. Despite this lack of specific termination sites, during stages 12 and 13 a greater increase is seen in copy number to one side of ACE3, and it was often observe by immunofluorescence that one of the two bars is shorter. This suggests that the sequence or chromatin structure to the other side of ACE3 hinders fork movement, and as fewer forks move out, less BrdU incorporation occurs and a shorter bar results (Claycomb, 2002).
These studies highlight the complex regulation of chorion gene amplification. How are the number of origin firings restricted to the proper developmental time? It is known that the number of rounds of origin firing at the chorion amplicons is limited by the action of Rb, E2F1, and DP. Perhaps Dup and MCM2-7 are also a part of this regulation, with origins firing only when MCM2-7 are properly loaded. It will also be interesting to decipher the regulation of Dup/Cdt1 during amplification. Recent studies have demonstrated that a Drosophila homologue of the metazoan re-replication inhibitor, Geminin, exists and interacts biochemically and genetically with Dup/Cdt1. Female-sterile mutations in geminin result in increased BrdU incorporation during amplification, raising the possibility that Geminin acts on DUP/Cdt1 at the chorion loci to limit origin firing. In addition to permitting the delineation of the regulatory circuitry controlling origin firing, the ability to developmentally distinguish initiation from elongation provides a powerful tool for the analysis of the properties of metazoan replication factors in vivo (Claycomb, 2002).
The MCM2-7 proteins are crucial components of the pre replication complex (preRC) in eukaryotes. Since they are significantly more abundant than other preRC components, it was of interest to determining whether the entire cellular content was necessary for DNA replication in vivo. A systematic depletion of the MCM proteins was performed in Drosophila S2 cells using dsRNA-interference. Reducing MCM2-6 levels by >95-99% had no significant effect on cell cycle distribution or viability. Depletion of MCM7 however caused an S-phase arrest. MCM2-7 depletion produced no change in the number of replication forks as measured by PCNA loading. Depletion of MCM8 caused a 30% reduction in fork number, but no significant effect on cell cycle distribution or viability. No additive effects were observed by co-depleting MCM8 and MCM5. These studies suggest that, in agreement with what has previously been observed for Xenopus in vitro, not all of the cellular content of MCM2-6 proteins is needed for normal cell cycling. They also reveal an unexpected unique role for MCM7. Finally they suggest that MCM8 has a role in DNA replication in S2 cells (Crevel, 2007).
Although this study could demonstrate specificity of the RNAi depletions, co-instability was observed for certain combinations of MCM proteins. Some of observations can be explained based on the composition of reported MCM sub-complexes. Therefore, a reduction in MCM5 when MCM3 is targeted, and MCM4 when MCM6 and MCM7 are targeted might be related to loss of stability of the MCM3/5 and MCM4/6/7 complexes. However this is not a complete explanation since MCM3 stability is unaffected by MCM5 depletion and MCM6/7 are not affected by depletion of other MCM4/6/7 components. In addition, MCM2, which is affected by MCM6 depletion, is not thought to be a component of either complex. The co-reductions cannot be rationalized based on models proposed for the structure of the MCM hexameric complex. Although the basis for the co-reductions is not understood, it was shown that they did not occur via the proteosome pathway since treatment with proteosome inhibitors had no effect. Co-instability of MCM proteins has been reported in other systems, but the reported combinations differ from those observed in Drosophila (Crevel, 2007).
Secondly the data suggest that a dramatic reduction in the level of MCM2-6 and 8 in vivo in Drosophila S2 cells has little apparent effect on cell survival and DNA replication. This therefore suggests that the MCM paradox - originally observed in Xenopus cell free extracts - can also be observed in vivo for Drosophila. Cell viability has also previously been shown to be unaffected for MCM2 and 5 depletions in Drosophila Kc cells. Whether the same effects will also be seen in other higher eukaryotes is unclear and in fact it has been reported that human cells cannot traverse S if MCM4 is depleted (Ekholm-Reed, 2004). Since it is unlikely that the lack of replication effects on depletion of MCM2-6 is due to a different role for the MCM complex in Drosophila, two other possibilities are suggested. Firstly, consistent with what has been suggested for Xenopus it might be that under normal circumstances most of the MCM protein in cells is redundant. It is estimated that there are 50-100 MCM complexes per origin (assuming origin spacing of 40-100 kb) in S2 cells. Therefore even cells which have lost 99% of a specific MCM should have enough protein to ensure that most origins have one MCM complex. A single MCM complex per origin may therefore be sufficient to allow a full complement of activated replication forks as measured by PCNA loading. In this case the results support proposed MCM mechanisms involving single or double hexamers rather than those that require bulk chromatin loading of MCMs. Perhaps in support of this suggestion no effects are seen of the MCM depletion on cdc45 chromatin loading. Cdc45 has been suggested to form an active component of the replicative helicase complex with GINS and MCM proteins (Moyer, 2006). It is therefore possible that despite the drastic reduction in the total number of MCM complexes in the dsRNA treated S2 cells the total number of active helicases has not altered (Crevel, 2007).
The second possibility is that MCM loss is compensated for by other proteins. Whether MCM8 could perform this function was investigated. The decrease in PCNA loading observed on depletion of MCM8 suggests that Drosophila MCM8 does play a role in replication. From these data the exact nature of its role is unclear, however the lack of an effect of the depletion on cdc45 loading suggests that unlike the MCM2-7 proteins it is unlikely to be required for the loading of downstream initiation factors. In addition MCM8 cannot be the MCM2-6 compensating protein since co-depletion of MCM5 and MCM8 does not synergistically affect cell viability or DNA replication (Crevel, 2007).
Finally the differences observed between depletion of MCM7 and MCM2-6 suggest that not all MCM proteins are equivalent. The mechanism behind this differential behaviour is not clear. Although a complex of MCM4/6/7 has been shown to have helicase activity, there is no evidence that MCM7 acts independently. Therefore MCM7 may have additional cellular functions. A role for MCM7 as a damage sensor via the ATR pathway has been suggested by work in human and S. cerevisiae cells where depletion or mutation of MCM7 produces cells defective in the UV-induced S-phase checkpoint. In Xenopus extracts MCM7 has also been shown to bind to the Rb protein leading to a brake on DNA replication. It is possible that the MCM7 effect that was observed is related to a failure of a negative control. This could lead to more significant damage which activates other checkpoints to cause the S phase stop. How this might be related to the roles of the S.cerevisiae and human MCM7 protein in the UV checkpoint is unclear since RNAi depletion of human MCM7 was not reported to show this effect. The level of MCM7 protein remaining after depletion is significantly higher in human than Drosophila cells, however less efficient depletion of Drosophila MCM7 has been seen to produce the same effect. Alternatively in addition to acting as a negative regulator of replication, MCM7 may have a positive regulatory effect on replication. In either case the effect is likely to involve MCM7 directly, rather than occurring as a secondary effect of a replication defect, since similar effects are not observed for other MCM proteins (Crevel, 2007).
Botchan, M. (1996). Coordinating DNA replication with cell division: Current status of the licensing concept. Proc. Natl. Acad. Sci. 93: 9997-10000. PubMed Citation: 8816736
Brown, G. W. and Kelly, T. J. (1999a). Purification of Hsk1, a minichromosome maintenance protein kinase
from fission yeast. J. Biol. Chem. 273(34): 22083-90. PubMed Citation: 9705352
Brown, G. W. and Kelly, T. J. (1999b). Cell cycle regulation of Dfp1, an activator of the Hsk1 protein kinase. Proc. Natl. Acad. Sci. 96(15): 8443-8. PubMed Citation: 10411894
Chen, S., de Vries, M. A. and Bell, S. P. (2007). Orc6 is required for dynamic recruitment of Cdt1 during repeated Mcm2-7 loading. Genes Dev. 2007 21(22): 2897-907. PubMed citation: 18006685
Chong, J. P. J., Thömmes, P and Blow, J. J. (1996). The role of MCM/P1 proteins in licensing of DNA replication. Trends in Biochem. Sci. 21: 102-106. PubMed Citation: 8882583
Chong, J. P., et al. (2000). A double-hexamer archaeal minichromosome maintenance protein is an ATP-dependent DNA helicase. Proc. Natl. Acad. Sci. 97(4): 1530-5. PubMed Citation: 10677495
Claycomb, J. M., et al. (2002). Visualization of replication initiation and elongation in Drosophila, Jour. Cell Biol. 159: 225-236. 12403810
Coleman, T. R., Carpenter, P. B. and Dunphy, W. G. (1996). The Xenopus Cdc6 protein is essential for the initiation of a single round of DNA replication in cell-free extracts. Cell 87: 53-63. PubMed Citation: 8858148
Cook, J. G., et al. (2002). Analysis of Cdc6 function in the assembly of mammalian prereplication complexes. Proc. Natl. Acad. Sci. 99(3): 1347-52. 11805305
Cook, J. G., Chasse, D. A. and Nevins, J. R. (2004). The regulated association of Cdt1 with minichromosome maintenance proteins and Cdc6 in mammalian cells.
J. Biol. Chem. 279(10): 9625-33. 14672932
Costa, A., (2011). The structural basis for MCM2-7 helicase activation by GINS and Cdc45. Nat. Struct. Mol. Biol. 18(4): 471-7. PubMed Citation: 21378962
Coué, M., Kearsey, S. E. and Mechali, M. (1996). Chromatin binding, nuclear localization and phosphorylation of Xenopus
cdc21 are cell-cycle dependent and associated with the control of
initiation of DNA replication. EMBO J. 15: 1085-1097
Coverley, D., et al. (1998). Protein kinase inhibition in G2 causes mammalian Mcm proteins to
reassociate with chromatin and restores ability to replicate. Exp. Cell Res. 238(1): 63-69
Crevel, G., et al. (2007). Differential requirements for MCM proteins in DNA replication in Drosophila S2 cells. PLoS ONE 2(9): e833. PubMed citation: 17786205
Diffley, J. F. (2009). Concerted loading of Mcm2-7 double hexamers around DNA during DNA replication origin licensing. Cell 139(4): 719-30. PubMed Citation: 19896182
Dominguez-Sola, D., et al. (2007). Non-transcriptional control of DNA replication by c-Myc. Nature 448: 445-451. PubMed Citation: 17597761
Ekholm-Reed, S., Mendez, J., Tedesco, D., Zetterberg, A., Stillman, B., et al. (2004). Deregulation of cyclin E in human cells interferes with prereplication complex assembly. J. Cell Biol. 165: 789-800. PubMed citation: 15197178
Feger, G., et al. (1995). dpa, a member of the MCM family, is required for mitotic DNA replication but not endoreplication in Drosophila. EMBO J. 14: 5387-98. PubMed Citation: 7489728
Francis, L. I., Randell, J. C., Takara, T. J., Uchima, L. and Bell, S. P. (2009). Incorporation into the prereplicative complex activates the Mcm2-7 helicase for Cdc7-Dbf4 phosphorylation. Genes Dev. 23(5): 643-54. PubMed Citation: 19270162
Fujita, M., et al. (1998). Cell cycle- and chromatin binding state-dependent phosphorylation of
human MCM heterohexameric complexes. A role for cdc2 kinase.
J. Biol. Chem. 273(27): 17095-101
Ge, X. Q., Jackson, D. A. and Blow, J. J. (2007). Dormant origins licensed by excess Mcm2-7 are required for human cells to survive replicative stress. Genes Dev. 21(24): 3331-41. PubMed citation: 18079179
Grandori, C., et al. (2003). Werner syndrome protein limits MYC-induced cellular senescence. Genes Dev. 17(13): 1569-74. PubMed Citation: 12842909
Hardy, C. F., et al. (1997). mcm5/cdc46-bob1 bypasses the requirement for the S phase
activator Cdc7p. Proc. Natl. Acad. Sci. 94(7): 3151-5
Hassan, B. and Vaessin, H. (1997). Daughterless is required for the expression of cell cycle genes in peripheral nervous system precursors of Drosophila embryos. Dev. Genet. 21(2): 117-122. PubMed Citation: 9332970
Hill, A. L., Phelan, S. A. and Loeken, M. R. (1998). Reduced expression of pax-3 is associated with overexpression of
cdc46 in the mouse embryo. Dev. Genes Evol. 208(3): 128-34
Hodgson, B., et al. (2002). Geminin becomes activated as an inhibitor of Cdt1/RLF-B following nuclear import. Curr. Biol. 12: 678-683. 11967157
Hua, X. H. and Newport, J. (1998). Identification of a preinitiation step in DNA replication that is
independent of origin recognition complex and cdc6, but dependent
on cdk2. J. Cell Biol. 140(2): 271-281
Iwabuchi, M., et al. (2002). Coordinated regulation of M Phase exit and
S phase entry by the Cdc2 activity level in the early embryonic cell cycle. Dev. Biol. 243: 34-43. 11846475
Ishimi, Y. (1997). A DNA helicase activity is associated with an MCM4, -6, and -7 protein complex. J. Biol. Chem. 272(39): 24508-13
Ishimi, Y., et al. (1998). Biochemical function of mouse minichromosome maintenance 2 protein. J. Biol. Chem. 273(14): 8369-75
Ishimi, Y., et al. (2000). Inhibition of Mcm4,6,7 helicase activity by phosphorylation with cyclin A/Cdk2. J. Biol. Chem. 275(21): 16235-41.
Jiang, W., et al. (1999). Mammalian Cdc7-Dbf4 protein kinase
complex is essential for initiation of DNA
replication. EMBO J. 18: 5703-5713
Kearsey, S. E., et al. (2000). Chromatin binding of the fission yeast replication factor mcm4
occurs during anaphase and requires ORC and cdc18. EMBO J. 19: 1681-1690
Kelman, Z., Lee, J. K. and Hurwitz, J. (1999). The single minichromosome maintenance protein of Methanobacterium thermoautotrophicum
DeltaH contains DNA helicase activity. Proc. Natl. Acad. Sci. 96(26): 14783-8.
Lei, M., et al. (1997). Mcm2 is a target of regulation by Cdc7-Dbf4 during the initiation of
DNA synthesis. Genes Dev. 11(24): 3365-3374
Liang, C. and Stillman, B. (1997). Persistent initiation of DNA replication and chromatin-bound MCM
proteins during the cell cycle in cdc6 mutants. Genes Dev. 11(24): 3375-3386
Liang, D. T., Hodson, J. A. and Forsburg, S. L. (1999). Reduced dosage of a single fission yeast MCM protein causes genetic instability and S phase delay. J. Cell Sci. 112 (Pt 4): 559-67
Madine, M. A., et al. (1995a). MCM3 complex required for cell cycle regulation of DNA replication in
vertebrate cells. Nature 3755: 421-424
Madine, M. A., et al. (1995b). The nuclear envelope prevents reinitiation of replication by regulating
the binding of MCM3 to chromatin in Xenopus egg extracts. Curr. Biol. 5: 1270-1279
Maiorano, D., Van Assendelft, G. B. and Kearsey, S. E. (1996). Fission yeast cdc21, a member of the MCM protein family, is required
for onset of S phase and is located in the nucleus throughout the cell
cycle. EMBO J. 15: 861-872
Maiorano, D., Moreau, J. and Mechali, M. (2000). XCDT1 is required for the assembly of pre-replicative complexes in Xenopus
laevis. Nature 404(6778): 622-5.
Mizushima, T., Takahashi, N. and Stillman, B. (2000). Cdc6p modulates the structure and DNA binding activity of the origin
recognition complex in vitro. Genes Dev. 14: 1631-1641.
Moyer, S. E., Lewis, P. W., Botchan, M. R. (2006). Isolation of the Cdc45/Mcm2-7/GINS (CMG) complex, a candidate for the eukaryotic DNA replication fork helicase. Proc. Natl. Acad. Sci. 103: 10236-10241. PubMed citation: 16798881
Nakatsuru, S., Sudo, K. and Nakamura, Y. (1995). Isolation and mapping of a human gene (MCM2) encoding a product
homologous to yeast proteins involved in DNA replication. Cytogenet. Cell Genet. 68: 226-230
Nguyen, V. Q., et al. (2000). Clb/Cdc28 kinases promote nuclear export of the replication initiator proteins Mcm2-7
Curr. Biol. 10: 195-205
Nishitani, H., et al. (2000). The Cdt1 protein is required to license DNA for replication in fission yeast. Nature 404(6778): 625-8.
Pacek, M., et al. (2006). Localization of MCM2-7, Cdc45, and GINS to the site of DNA unwinding during eukaryotic DNA replication. Mol. Cell 21(4): 581-7. Medline abstract: 16483939
Rowles, A., et al. (1996). Interaction between the origin recognition complex and the replication licensing system in Xenopus. Cell 87: 287-296
Sato, M., et al. (2000). Electron microscopic observation and single-stranded DNA binding activity of the Mcm4,6,7 complex. J. Mol. Biol. 300(3): 421-31.
Sible, J. C., et al. (1998). Developmental regulation of MCM replication factors in Xenopus
laevis. Curr. Biol. 8(6): 347-350
Su, T.T., Feger, G. and O'Farrell, P.H. (1996). Drosophila MCM protein complexes. Molec. Biol. Cell 7: 319-329. PubMed Citation: 8688561
Su, T. T. and O'Farrell, P. H. (1997). Chromosome association of minichromosome maintenance
proteins in Drosophila mitotic cycles. J. Cell Biol. 139(1): 13-21. PubMed Citation: 9314525
Su, T. T. and O'Farrell, P. H. (1998). Chromosome association of minichromosome maintenance proteins
in Drosophila endoreplication cycles. J. Cell Biol. 140(3): 451-460. PubMed Citation: 9456309
Schwacha, A. and Bell, S. P. (2001). Interactions between two catalytically distinct MCM subgroups are essential for coordinated ATP hydrolysis and DNA replication. Molec. Cell 8: 1093-1104. 11741544
Tada, S., et al. (1999). The RLF-B component of the replication licensing system is distinct from cdc6 and functions after cdc6 binds to chromatin. Curr. Biol. 9(4): 211-4.
Tanaka, S., and Diffley, J.F. (2002). Interdependent nuclear accumulation of budding yeast Cdt1 and Mcm2-7 during G1 phase. Nat. Cell Biol. 4: 198-207. 11836525
Thommes, P., et al. (1997). The RLF-M component of the replication licensing system forms
complexes containing all six MCM/P1 polypeptides. EMBO J. 16(11): 3312-9
Treisman, J. E., et al. (1995). Cell proliferation and DNA replicaion defects in a Drosophila MCM2 mutant. Genes Dev. 9: 1709-15. PubMed Citation: 7622035
Whitebread, L. A. and Dalton, S. (1995). Cdc54 belongs to the Cdc46/Mcm3 family of proteins which are
essential for initiation of eukaryotic DNA replication. Gene 155: 113-117
Weinreich, M., Liang, C. and Stillman, B. (1999). The cdc6p nucleotide-binding motif is required for loading
mcm proteins onto chromatin. Proc. Natl. Acad. Sci. 96(2): 441-6
Yan, H., Merchant, A. M. and Tye, B. K. (1993). Cell cycle-regulated nuclear localization of MCM2 and MCM3, which
are required for the initiation of DNA synthesis at chromosomal
replication origins in yeast. Genes Dev. 7: 2149-60
You, Z., et al. (1999). Biochemical analysis of the intrinsic Mcm4-Mcm6-mcm7 DNA helicase activity. Mol. Cell. Biol. 19(12): 8003-15.
disc proliferation abnormal:
Biological Overview
| Evolutionary Homologs
| Regulation
| Developmental Biology
date revised: 28 December 2011
Home page: The Interactive Fly © 1997 Thomas B. Brody, Ph.D.
The Interactive Fly resides on the
Society for Developmental Biology's Web server.