Background: MCM2-7 loading onto chromatin licenses origins for replication. Results: MCMs exhibit transient interactions with chromatin in late mitosis, stable binding in G 1 phase and increased loading in late G 1 phase. Conclusion: Multilevel regulation of MCM2-7 loading to chromatin occurs during mitosis and preceding the G 1 /S phase transition. Significance: The dynamics of the DNA licensing system within live human cells reveal multiple control points.
Background:The licensing inhibitor geminin must be regulated to ensure once per cell cycle replication. Results: Geminin is spatially and temporally controlled by nuclear exclusion during part of the G 1 phase in human cells. Conclusion: Geminin exclusion from the nucleus provides an additional level of licensing control, balancing the Cdt1/geminin ratio. Significance: Multiple overlapping mechanisms are used by human cells to ensure genome stability.
Copy Number Gains (CNGs) lead to genetic heterogeneity, driving evolution and carcinogenesis. The mechanisms promoting CNG formation however remain poorly characterized. We show that abnormal expression of the replication licensing factor Cdc18 in fission yeast, which leads to genome-wide re-replication, drives the formation of CNGs at different genomic loci, promoting the acquisition of new selectable traits. Whole genome sequencing reveals Mb long, primarily extrachromosomal amplicons. Genetic analysis shows that homology-mediated repair is required to resolve re-replication intermediates into heritable CNGs. Consistently, we show that in mammalian cells overexpression of CDC6 and/or CDT1 leads to CNGs and promotes drug resistance. In human cells, multiple repair pathways are activated upon rereplication and act antagonistically, with RAD52 promoting and 53BP1 inhibiting CNG formation. In tumours, CDT1 and/or CDC6 overexpression correlates with copy number gains genome-wide. We propose re-replication as an evolutionary-conserved driver of CNGs, highlighting a link between aberrant licensing, CNGs and cancer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.