scholarly journals Drosophila Minichromosome Maintenance 6 Is Required for Chorion Gene Amplification and Genomic Replication

2002 ◽  
Vol 13 (2) ◽  
pp. 607-620 ◽  
Author(s):  
Gina Schwed ◽  
Noah May ◽  
Yana Pechersky ◽  
Brian R. Calvi
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Genetic Dissection ◽  
Minichromosome Maintenance ◽  
Multiple Origins ◽  
Origin Licensing ◽  
Mcm Complex ◽  
Mcm Proteins ◽  
Prereplicative Complex ◽  
Cycle Regulation

Duplication of the eukaryotic genome initiates from multiple origins of DNA replication whose activity is coordinated with the cell cycle. We have been studying the origins of DNA replication that control amplification of eggshell (chorion) genes duringDrosophila oogenesis. Mutation of genes required for amplification results in a thin eggshell phenotype, allowing a genetic dissection of origin regulation. Herein, we show that one mutation corresponds to a subunit of the minichromosome maintenance (MCM) complex of proteins, MCM6. The binding of the MCM complex to origins in G1 as part of a prereplicative complex is critical for the cell cycle regulation of origin licensing. We find that MCM6 associates with other MCM subunits during amplification. These results suggest that chorion origins are bound by an amplification complex that contains MCM proteins and therefore resembles the prereplicative complex. Lethal alleles of MCM6 reveal it is essential for mitotic cycles and endocycles, and suggest that its function is mediated by ATP. We discuss the implications of these findings for the role of MCMs in the coordination of DNA replication during the cell cycle.

Cdc7p-Dbf4p becomes famous in the cell cycle

2000 ◽  
Vol 113 (12) ◽  
pp. 2111-2117 ◽  
Author(s):  
R.A. Sclafani
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Cancer Progression ◽  
Regulatory Subunit ◽  
Mcm Helicase ◽  
Great Insight ◽  
Early Biomarker ◽  
Mcm Complex ◽  
Eukaryotic Organisms ◽  
Cycle Regulation

Great insight into the molecular details of cell cycle regulation has been obtained in the past decade. However, most of the progress has been in defining the regulation of the family of cyclin-dependent kinases (CDKs). Recent studies of a myriad of eukaryotic organisms have defined both the regulation and substrates of Cdc7p kinase, which forms a CDK-cyclin-like complex with Dbf4p, is necessary for the initiation of DNA replication and has been conserved in evolution. This kinase is also required for the induction of mutations after DNA damage and for commitment to recombination in the meiotic cell cycle. However, less is known about the role of the kinase in these processes. In a manner similar to CDKs, Cdc7p is activated by a regulatory subunit, Dbf4, the levels of which fluctuate during the cell cycle. One or more subunits of the conserved MCM helicase complex at chromosomal origins of DNA replication are substrates for the kinase during S phase. Phosphorylation of the MCM complex by Cdc7p-Dbf4p might activate DNA replication by unwinding DNA. Therefore, activation of Cdc7p is required for DNA replication. Given that Cdc7p-Dbf4 kinase is overexpressed in many neoplastic cells and tumors, it might be an important early biomarker during cancer progression.

scholarly journals Minichromosome Maintenance Proteins Cooperate with LANA during the G1/S Phase of the Cell Cycle To Support Viral DNA Replication

2019 ◽  
Vol 93 (7) ◽  
Author(s):  
Prerna Dabral ◽  
Timsy Uppal ◽  
Cyprian C. Rossetto ◽  
Subhash C. Verma
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Viral Genome ◽  
Minichromosome Maintenance ◽  
Viral Origin ◽  
Terminal Domain ◽  
Mcm Complex ◽  
Cellular Replication ◽  
Cellular Dna

ABSTRACTLatency-associated nuclear antigen (LANA) is essential for maintaining the viral genome by regulating replication and segregation of the viral episomes. The virus maintains 50 to 100 episomal copies during latency and replicates in synchrony with the cellular DNA of the infected cells. Since virus lacks its own replication machinery, it utilizes the cellular proteins for replication and maintenance, and LANA has been shown to make many of these proteins available for replication by directly recruiting them to the viral origin of replication within the terminal repeat (TR) region. Our studies identified members of the minichromosome maintenance (MCM) complex as potential LANA-interacting proteins. Here, we show that LANA specifically interacts with the components of the MCM complex, primarily during the G1/S phase of the cell cycle. MCM3 and -4 of the MCM complex specifically bound to the amino-terminal domain, while MCM6 bound to both the amino- and carboxyl-terminal domains of LANA. The MCM binding region in the N-terminal domain mapped to the chromatin binding domain (CBD). LANA with point mutations in the carboxyl-terminal domain identified an MCM6 binding domain, and overexpression of that domain (amino acids [aa] 1100 to 1150) abolished TR replication. Introduction of a peptide encompassing the LANA aa 1104 to 1123 reduced MCM6 association with LANA and TR replication. Moreover, a recombinant Kaposi’s sarcoma-associated herpesvirus (KSHV) expressing LANA with a deletion of aa 1100 to 1150 (BAC16Δ1100–1150, where BAC is bacmid) showed reduced replication and persistence of viral genome copies compared to levels with the wild-type BAC16. Additionally, the role of MCMs in viral replication was confirmed by depleting MCMs and assaying transient and long-term maintenance of the viral episomes. The recruitment of MCMs to the replication origins through LANA was demonstrated through chromatin immunoprecipitation and isolation of proteins on nascent replicated DNA (iPOND). These data clearly show the role of MCMs in latent DNA replication and the potential for targeting the C-terminal domain of LANA to block viral persistence.IMPORTANCELANA-mediated latent DNA replication is essential for efficient maintenance of KSHV episomes in the host. During latency, virus relies on the host cellular machinery for replication, which occurs in synchrony with the cellular DNA. LANA interacts with the components of multiple cellular pathways, including cellular replication machinery, and recruits them to the viral origin for DNA replication. In this study, we characterize the interactions between LANA and minichromosome maintenance (MCM) proteins, members of the cellular replication complex. We demonstrated a cell cycle-dependent interaction between LANA and MCMs and determined their importance for viral genome replication and maintenance through biochemical assays. In addition, we mapped a 50-amino acid region in LANA which was capable of abrogating the association of MCM6 with LANA and blocking DNA replication. We also detected LANA along with MCMs at the replication forks using a novel approach, isolation of proteins on nascent DNA (iPOND).

scholarly journals Nascent Transcription of MCM2-7 Is Important for Nuclear Localization of the Minichromosome Maintenance Complex in G1

2007 ◽  
Vol 18 (4) ◽  
pp. 1447-1456 ◽  
Author(s):  
Katherine A. Braun ◽  
Linda L. Breeden
Keyword(s):  
Cell Cycle ◽  
Nuclear Localization ◽  
Nuclear Import ◽  
S Phase ◽  
Cyclin Dependent Kinase ◽  
Minichromosome Maintenance ◽  
Mcm Complex ◽  
Mcm Proteins ◽  
Constitutive Production ◽  
New Protein

The minichromosome maintenance genes (MCM2-7) are transcribed at M/G1 just as the Mcm complex is imported into the nucleus to be assembled into prereplication complexes, during a period of low cyclin-dependent kinase (CDK) activity. The CDKs trigger DNA replication and prevent rereplication in part by exporting Mcm2-7 from the nucleus during S phase. We have found that repression of MCM2-7 transcription in a single cell cycle interferes with the nuclear import of Mcms in the subsequent M/G1 phase. This suggests that nascent Mcm proteins are preferentially imported into the nucleus. Consistent with this, we find that loss of CDK activity in G2/M is not sufficient for nuclear import, there is also a requirement for new protein synthesis. This requirement is not met by constitutive production of Cdc6 and does not involve synthesis of new transport machinery. The Mcm proteins generated in the previous cell cycle, which are unable to reaccumulate in the nucleus, are predominantly turned over by ubiquitin-mediated proteolysis in late mitosis/early G1. Therefore, the nuclear localization of Mcm2-7 is dependent on nascent transcription and translation of Mcm2-7 and the elimination of CDK activity which occurs simultaneously as cells enter G1.

scholarly journals Chromosome Association of Minichromosome Maintenance Proteins in Drosophila Endoreplication Cycles

1998 ◽  
Vol 140 (3) ◽  
pp. 451-460 ◽  
Author(s):  
Tin Tin Su ◽  
Patrick H. O'Farrell
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Mitotic Cell ◽  
Chromosome Association ◽  
Minichromosome Maintenance ◽  
Chromosome Duplication ◽  
Chromosome Associations ◽  
Mcm Proteins ◽  
Polytene Nuclei ◽  
Replication Factors

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. We examined the behavior of MCM proteins in endoreplicating larval salivary glands, to determine whether oscillation of MCM–chromosome localization occurs in conjunction with passage through an endocycle S phase. We found that MCMs in polytene nuclei exist in two states: associated with or dissociated from chromosomes. We demonstrate that cyclin E can drive chromosome association of DmMCM2 and that DNA synthesis erases this association. We conclude that mitosis is not required for oscillations in chromosome binding of MCMs and propose that cycles of MCM–chromosome association normally occur in endocycles. These results are discussed in a model in which the cycle of MCM–chromosome associations is uncoupled from mitosis because of the distinctive program of cyclin expression in endocycles.

scholarly journals Intrinsic checkpoint deficiency during cell cycle re-entry from quiescence

2019 ◽  
Author(s):  
Jacob Peter Matson ◽  
Amy M. House ◽  
Gavin D. Grant ◽  
Huaitong Wu ◽  
Joanna Perez ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Genome Instability ◽  
Replication Stress ◽  
S Phase ◽  
Minichromosome Maintenance ◽  
Cell Cycle Entry ◽  
Origin Licensing ◽  
Dna Replication Origin ◽  
Dna Replication Origins

SUMMARYThe authors find that human cells re-entering the cell cycle from quiescence have both an impaired p53-dependent DNA replication origin licensing checkpoint and slow origin licensing. This combination makes every first S phase underlicensed and hypersensitive to replication stress.ABSTRACTTo maintain tissue homeostasis, cells transition between cell cycle quiescence and proliferation. An essential G1 process is Minichromosome Maintenance complex (MCM) loading at DNA replication origins to prepare for S phase, known as origin licensing. A p53-dependent origin licensing checkpoint normally ensures sufficient MCM loading prior to S phase entry. We used quantitative flow cytometry and live cell imaging to compare MCM loading during the long first G1 upon cell cycle entry and the shorter G1 phases in the second and subsequent cycles. We discovered that despite the longer G1 phase, the first G1 after cell cycle re-entry is significantly underlicensed. As a result, the first S phase cells are hypersensitive to replication stress. This underlicensing is from a combination of slow MCM loading with a severely compromised origin licensing checkpoint. The hypersensitivity to replication stress increases over repeated rounds of quiescence. Thus, underlicensing after cell cycle re-entry from quiescence distinguishes a higher risk cell cycle that promotes genome instability.

scholarly journals Targeting Non-Oncogene Addiction for Cancer Therapy

Biomolecules ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 129
Author(s):  
Hae Ryung Chang ◽  
Eunyoung Jung ◽  
Soobin Cho ◽  
Young-Jun Jeon ◽  
Yonghwan Kim
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Cancer Therapy ◽  
Cell Cycle Regulation ◽  
Synthetic Lethality ◽  
Current Knowledge ◽  
Cancer Therapies ◽  
Oncogene Addiction ◽  
Clinical Biomarkers ◽  
Cycle Regulation

While Next-Generation Sequencing (NGS) and technological advances have been useful in identifying genetic profiles of tumorigenesis, novel target proteins and various clinical biomarkers, cancer continues to be a major global health threat. DNA replication, DNA damage response (DDR) and repair, and cell cycle regulation continue to be essential systems in targeted cancer therapies. Although many genes involved in DDR are known to be tumor suppressor genes, cancer cells are often dependent and addicted to these genes, making them excellent therapeutic targets. In this review, genes implicated in DNA replication, DDR, DNA repair, cell cycle regulation are discussed with reference to peptide or small molecule inhibitors which may prove therapeutic in cancer patients. Additionally, the potential of utilizing novel synthetic lethal genes in these pathways is examined, providing possible new targets for future therapeutics. Specifically, we evaluate the potential of TONSL as a novel gene for targeted therapy. Although it is a scaffold protein with no known enzymatic activity, the strategy used for developing PCNA inhibitors can also be utilized to target TONSL. This review summarizes current knowledge on non-oncogene addiction, and the utilization of synthetic lethality for developing novel inhibitors targeting non-oncogenic addiction for cancer therapy.

scholarly journals Regulation of Replication Licensing by Acetyltransferase Hbo1

2006 ◽  
Vol 26 (3) ◽  
pp. 1098-1108 ◽  
Author(s):  
Masayoshi Iizuka ◽  
Tomoko Matsui ◽  
Haruhiko Takisawa ◽  
M. Mitchell Smith
Keyword(s):  
Dna Replication ◽  
Origin Recognition Complex ◽  
Cyclin Dependent Kinase ◽  
Chromatin Binding ◽  
Regulatory Factor ◽  
Minichromosome Maintenance ◽  
Egg Extracts ◽  
Sequential Binding ◽  
Initiation Of Dna Replication ◽  
Prereplicative Complex

ABSTRACT The initiation of DNA replication is tightly regulated in eukaryotic cells to ensure that the genome is precisely duplicated once and only once per cell cycle. This is accomplished by controlling the assembly of a prereplicative complex (pre-RC) which involves the sequential binding to replication origins of the origin recognition complex (ORC), Cdc6/Cdc18, Cdt1, and the minichromosome maintenance complex (Mcm2-Mcm7, or Mcm2-7). Several mechanisms of pre-RC regulation are known, including ATP utilization, cyclin-dependent kinase levels, protein turnover, and Cdt1 binding by geminin. Histone acetylation may also affect the initiation of DNA replication, but at present neither the enzymes nor the steps involved are known. Here, we show that Hbo1, a member of the MYST histone acetyltransferase family, is a previously unrecognized positive regulatory factor for pre-RC assembly. When Hbo1 expression was inhibited in human cells, Mcm2-7 failed to associate with chromatin even though ORC and Cdc6 loading was normal. When Xenopus egg extracts were immunodepleted of Xenopus Hbo1 (XHbo1), chromatin binding of Mcm2-7 was lost, and DNA replication was abolished. The binding of Mcm2-7 to chromatin in XHbo1-depleted extracts could be restored by the addition of recombinant Cdt1.

Essential role of human CDT1 in DNA replication and chromatin licensing

2002 ◽  
Vol 115 (7) ◽  
pp. 1435-1440 ◽  
Author(s):  
Mickael Rialland ◽  
Francesco Sola ◽  
Corrado Santocanale
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Complex Formation ◽  
Fission Yeast ◽  
Origin Recognition Complex ◽  
Essential Role ◽  
Large Body ◽  
Transformed Cells ◽  
Minichromosome Maintenance

Formation of pre-replicative complexes at origins is an early cell cycle event essential for DNA duplication. A large body of evidence supports the notion that Cdc6 protein, through its interaction with the origin recognition complex, is required for pre-replicative complex assembly by loading minichromosome maintenance proteins onto DNA. In fission yeast and Xenopus, this reaction known as the licensing of chromatin for DNA replication also requires the newly identified Cdt1 protein. We studied the role of hCdt1 protein in the duplication of the human genome by antibody microinjection experiments and analyzed its expression during the cell cycle in human non-transformed cells. We show that hCdt1 is essential for DNA replication in intact human cells, that it executes its function in a window of the cell cycle overlapping with pre-replicative complex formation and that it is necessary for the loading of minichromosome maintenance proteins onto chromatin. Intriguingly, we observed that hCdt1 protein, in contrast to other licensing factors, is already present in serum-deprived G0 arrested cells and its levels increase only marginally upon re-entry in the cell cycle.

scholarly journals Erratum to: Effects of flavonoids on expression of genes involved in cell cycle regulation and DNA replication in human fibroblasts

2016 ◽  
Vol 424 (1-2) ◽  
pp. 211-211
Author(s):  
Marta Moskot ◽  
Joanna Jakóbkiewicz-Banecka ◽  
Elwira Smolińska ◽  
Ewa Piotrowska ◽  
Grzegorz Węgrzyn ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Cell Cycle Regulation ◽  
Human Fibroblasts ◽  
Expression Of Genes ◽  
Cycle Regulation
Sign in / Sign up

Export Citation Format

Share Document