Millipore Sigma Vibrant Logo
 

minichrom+


60 Results Advanced Search  
Showing
Products (41)
Documents (16)
Site Content (3)

Narrow Your Results Use the filters below to refine your search

Document Type

  • (12)
  • (2)
  • (2)
Can't Find What You're Looking For?
Contact Customer Service

 

  • Minichromosome maintenance helicase paralog MCM9 is dispensible for DNA replication but functions in germ-line stem cells and tumor suppression. 21987787

    Effective DNA replication is critical to the health and reproductive success of organisms. The six MCM2-7 proteins, which form the replicative helicase, are essential for high-fidelity replication of the genome. Many eukaryotes have a divergent paralog, MCM9, that was reported to be essential for loading MCM2-7 onto replication origins in the Xenopus oocyte extract system. To address the in vivo role of mammalian MCM9, we created and analyzed the phenotypes of mice with various mutations in Mcm9 and an intronic DNA replication-related gene Asf1a. Ablation of Mcm9 was compatible with cell proliferation and mouse viability, showing that it is nonessential for MCM2-7 loading or DNA replication. Mcm9 mutants underwent p53-independent embryonic germ-cell depletion in both sexes, with males also exhibiting defective spermatogonial stem-cell renewal. MCM9-deficient cells had elevated genomic instability and defective cell cycle reentry following replication stress, and mutant animals were prone to sex-specific cancers, most notably hepatocellular carcinoma in males. The phenotypes of mutant mice and cells suggest that MCM9 evolved a specialized but nonessential role in DNA replication or replication-linked quality-control mechanisms that are especially important for germ-line stem cells, and also for tumor suppression and genome maintenance in the soma.
    Document Type:
    Reference
    Product Catalog Number:
    06-1295

  • Phosphorylation of minichromosome maintenance protein 7 (MCM7) by cyclin/cyclin-dependent kinase affects its function in cell cycle regulation. 23720738

    MCM7 is one of the subunits of the MCM2-7 complex that plays a critical role in DNA replication initiation and cell proliferation of eukaryotic cells. After forming the pre-replication complex (pre-RC) with other components, the MCM2-7 complex is activated by DDK/cyclin-dependent kinase to initiate DNA replication. Each subunit of the MCM2-7 complex functions differently under regulation of various kinases on the specific site, which needs to be investigated in detail. In this study, we demonstrated that MCM7 is a substrate of cyclin E/Cdk2 and can be phosphorylated on Ser-121. We found that the distribution of MCM7-S121A is different from wild-type MCM7 and that the MCM7-S121A mutant is much less efficient to form a pre-RC complex with MCM3/MCM5/cdc45 compared with wild-type MCM7. By using the Tet-On inducible HeLa cell line, we revealed that overexpression of wild-type MCM7 but not MCM7-S121A can block S phase entry, suggesting that an excess of the pre-RC complex may activate the cell cycle checkpoint. Further analysis indicates that the Chk1 pathway is activated in MCM7-overexpressed cells in a p53-dependent manner. We performed experiments with the human normal cell line HL-7702 and also observed that overexpression of MCM7 can cause S phase block through checkpoint activation. In addition, we found that MCM7 could also be phosphorylated by cyclin B/Cdk1 on Ser-121 both in vitro and in vivo. Furthermore, overexpression of MCM7-S121A causes an obvious M phase exit delay, which suggests that phosphorylation of MCM7 on Ser-121 in M phase is very important for a proper mitotic exit. These data suggest that the phosphorylation of MCM7 on Ser-121 by cyclin/Cdks is involved in preventing DNA rereplication as well as in regulation of the mitotic exit.
    Document Type:
    Reference
    Product Catalog Number:
    04-1521

  • Atorvastatin inhibits expression of minichromosome maintenance proteins in vascular smooth muscle cells. 12591091

    3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors have been reported to inhibit vascular smooth muscle cell growth, a key event in the pathogenesis of proliferative vascular diseases. The mechanism by which HMG-CoA reductase inhibitors exert their antiproliferative activity is not fully understood, especially their effect on DNA replication. We therefore investigated the effects of atorvastatin on minichromosome maintenance (MCM) protein 6 and 7 expression in vascular smooth muscle cells, two proteins essential for initiation of DNA replication. Stimulation of quiescent rat aortic vascular smooth muscle cells with fetal bovine serum induced MCM6 and MCM7 protein and mRNA expression, which was potently attenuated by atorvastatin in a dose-dependent fashion. Mevalonate completely abrogated the inhibitory effect on serum-induced MCM6 and MCM7 expression, demonstrating that biosynthesis of isoprenoids was likely the specific pathway blocked by atorvastatin. Transient transfection experiments revealed that atorvastatin inhibited MCM6 and MCM7 promoter activity, implicating a transcriptional mechanism. The MCM6 and MCM7 promoters contain several E2F sites critical for their transcriptional activation. Activity of a luciferase reporter plasmid containing four E2F elements was also strongly inhibited by atorvastatin. The inhibitory effect of atorvastatin on MCM6 and MCM7 was reversed by adenoviral-mediated overexpression of E2F, indicating that their downregulation by atorvastatin involves an E2F-dependent mechanism. These findings demonstrate that MCM proteins play an essential role during the proliferation of vascular smooth muscle cells and may provide a novel therapeutic target for proliferative vascular diseases. Inhibition of MCM6 and MCM7 expression by blocking E2F function may contribute importantly to the inhibition of vascular smooth muscle cell DNA synthesis by atorvastatin.
    Document Type:
    Reference
    Product Catalog Number:
    05-379
    Product Catalog Name:
    Anti-E2F-1 Antibody, clones KH20 and KH95

  • Mitogenic effects of the up-regulation of minichromosome maintenance proteins in anaplastic thyroid carcinoma. 15899946

    Anaplastic thyroid carcinomas (ATC) are among the most aggressive human malignancies and are characterized by high mitotic activity. Minichromosome maintenance proteins (MCM) 2-7 are required to initiate eukaryotic DNA replication, and their overexpression has been associated with dysplasia and malignancy.In an attempt to cast light on the mechanisms governing ATC, we evaluated MCM5 and MCM7 expression in human normal, papillary (PTC), and anaplastic thyroid samples, as well as in primary culture cells and transgenic mouse models.MCM5 and MCM7 expression was high in 65% of ATC and negligible in normal thyroid tissue and papillary thyroid carcinomas. In ATC, high MCM5 and MCM7 expression was paralleled by high levels of MCM2 and MCM6. An analysis of human ATC primary cell cultures and of a transgenic mouse model of ATC confirmed these findings. An increased transcription rate accounted for MCM7 up-regulation, because the activity of the MCM7 promoter was more than 10-fold higher in ATC cells compared with normal thyroid cells. Adoptive overexpression of wild-type p53, but not of its inactive (R248W and R273H) mutants, strongly down-regulated transcription from the MCM7 promoter, suggesting that p53 knock-out contributes to MCM7 up-regulation in ATC. Treatment with small inhibitory duplex RNAs, which decrease MCM7 protein levels, reduced the rate of DNA synthesis in ATC cells.MCM proteins are overexpressed in ATC and sustain the high proliferative capacity of ATC cells.
    Document Type:
    Reference
    Product Catalog Number:
    MAB424
    Product Catalog Name:
    Anti-PCNA Antibody, clone PC10

  • Chromatin association of human origin recognition complex, cdc6, and minichromosome maintenance proteins during the cell cycle: assembly of prereplication complexes in la ... 11046155

    Evidence obtained from studies with yeast and Xenopus indicate that the initiation of DNA replication is a multistep process. The origin recognition complex (ORC), Cdc6p, and minichromosome maintenance (MCM) proteins are required for establishing prereplication complexes, upon which initiation is triggered by the activation of cyclin-dependent kinases and the Dbf4p-dependent kinase Cdc7p. The identification of human homologues of these replication proteins allows investigation of S-phase regulation in mammalian cells. Using centrifugal elutriation of several human cell lines, we demonstrate that whereas human Orc2 (hOrc2p) and hMcm proteins are present throughout the cell cycle, hCdc6p levels vary, being very low in early G(1) and accumulating until cells enter mitosis. hCdc6p can be polyubiquitinated in vivo, and it is stabilized by proteasome inhibitors. Similar to the case for hOrc2p, a significant fraction of hCdc6p is present on chromatin throughout the cell cycle, whereas hMcm proteins alternate between soluble and chromatin-bound forms. Loading of hMcm proteins onto chromatin occurs in late mitosis concomitant with the destruction of cyclin B, indicating that the mitotic kinase activity inhibits prereplication complex formation in human cells.
    Document Type:
    Reference
    Product Catalog Number:
    ABE997

  • Rapamycin inhibits E2F-dependent expression of minichromosome maintenance proteins in vascular smooth muscle cells. 12646195

    Rapamycin inhibits vascular smooth muscle cell (VSMC) proliferation and rapamycin-eluting stents represent a novel therapeutic strategy for preventing postangioplasty restenosis. The precise molecular mechanism, for rapamycin-mediated inhibition of VSMC cell cycle progression and DNA replication remain to be elucidated. Minichromosome maintenance proteins (MCM) are essential regulators of DNA replication and the objective of this study was to examine the effect of rapamycin on their expression in rat aortic VSMC. Rapamycin substantially inhibited mitogen-induced MCM6 and MCM7 mRNA and protein expression in a dose-dependent fashion. Transient transfection experiments revealed that rapamycin inhibited MCM6 and MCM7 promoter activity, implicating a transcriptional mechanism. MCM6 and MCM7 transcriptional activation is regulated by E2F and activity of a luciferase reporter plasmid driven by four E2F elements was also significantly inhibited by rapamycin. The inhibitory effect of rapamycin on MCM6 and MCM7 was reversed by overexpression of E2F, indicating that their downregulation by rapamycin involves an E2F-dependent mechanism. These observations suggest that rapamycin inhibits MCM6 and MCM7 expression by blocking their E2F-dependent transactivation which may contribute importantly to the inhibition of VSMC DNA synthesis by rapamycin.
    Document Type:
    Reference
    Product Catalog Number:
    05-379
    Product Catalog Name:
    Anti-E2F-1 Antibody, clones KH20 and KH95