Reducing MCM levels in human primary T cells during the G0→G1 transition causes genomic instability during the first cell cycle

• Published in: Oncogene Vol. 29; no. 26; pp. 3803 - 3814
• Main Authors: Orr, S J, Gaymes, T, Ladon, D, Chronis, C, Czepulkowski, B, Wang, R, Mufti, G J, Marcotte, E M, Thomas, N S B
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-07-2010; Nature Publishing Group
• Subjects: 631/208/737/211; 631/250/1619/554; 631/337/1427; 631/45/612/1223; Apoptosis; Biological and medical sciences; Cell Biology; Cell cycle; Cell cycle, cell proliferation; Cell physiology; Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes; Cellular biology; CHK1 protein; CHK2 protein; Chromosome aberrations; Deoxyribonucleic acid; Diverse techniques; DNA; DNA biosynthesis; DNA damage; DNA repair; Fundamental and applied biological sciences. Psychology; Genomic instability; Genomics; Homologous recombination; Human Genetics; Internal Medicine; Lymphocytes T; Medicine; Medicine & Public Health; Metaphase; Molecular and cellular biology; Non-homologous end joining; Oncology; original-article; Replication origins; chromosomal abnormalities; premature chromatid separation; cell cycle; MCM; DNA damage; Human; Premature; Genomics; Carcinogenesis; DNA; Cell cycle; T-Lymphocyte; Chromatid; Instability; Lesion
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/onc.2010.138

DNA replication is tightly regulated, but paradoxically there is reported to be an excess of MCM DNA replication proteins over the number of replication origins. Here, we show that MCM levels in primary human T cells are induced during the G
0
→G
1
transition and are not in excess in proliferating cells. The level of induction is critical as we show that a 50% reduction leads to increased centromere separation, premature chromatid separation (PCS) and gross chromosomal abnormalities typical of genomic instability syndromes. We investigated the mechanisms involved and show that a reduction in MCM levels causes dose-dependent DNA damage involving activation of ATR & ATM and Chk1 & Chk2. There is increased DNA mis-repair by non-homologous end joining (NHEJ) and both NHEJ and homologous recombination are necessary for Mcm7-depleted cells to progress to metaphase. Therefore, a simple reduction in MCM loading onto DNA, which occurs in cancers as a result of aberrant cell cycle control, is sufficient to cause PCS and gross genomic instability within one cell cycle.