PCNA Retention on DNA into G2/M Phase Causes Genome Instability in Cells Lacking Elg1

Catherine Johnson,Vamsi K Gali,Tatsuro S Takahashi,Takashi Kubota

doi:10.1016/j.celrep.2016.06.030

Catherine Johnson, Vamsi K Gali + Show 2 more

Open Access

https://doi.org/10.1016/j.celrep.2016.06.030

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Journal: Cell Reports	Publication Date: Jun 30, 2016
Citations: 69	License type: cc-by

Affiliation: University of Aberdeen, Osaka University

Abstract

SummaryLoss of the genome maintenance factor Elg1 causes serious genome instability that leads to cancer, but the underlying mechanism is unknown. Elg1 forms the major subunit of a replication factor C-like complex, Elg1-RLC, which unloads the ring-shaped polymerase clamp PCNA from DNA during replication. Here, we show that prolonged retention of PCNA on DNA into G2/M phase is the major cause of genome instability in elg1Δ yeast. Overexpression-induced accumulation of PCNA on DNA causes genome instability. Conversely, disassembly-prone PCNA mutants that relieve PCNA accumulation rescue the genome instability of elg1Δ cells. Covalent modifications to the retained PCNA make only a minor contribution to elg1Δ genome instability. By engineering cell-cycle-regulated ELG1 alleles, we show that abnormal accumulation of PCNA on DNA during S phase causes moderate genome instability and its retention through G2/M phase exacerbates genome instability. Our results reveal that PCNA unloading by Elg1-RLC is critical for genome maintenance.

Highlights

Maintenance of the genome is crucial for all living organisms since loss of genome stability leads to mutations and chromosome rearrangements, causing cancers and other life-threatening diseases (Aguilera and Gomez-Gonzalez, 2008; Negrini et al, 2010)
Their ability to unload proliferating cell nuclear antigen (PCNA) was quantified by assessing PCNA present in chromatin fractions and using western blots of whole-cell extracts
The N-terminal domain of Elg1, which contains the small ubiquitin-related modifier (SUMO)-interacting motifs (SIMs), is not essential for methyl methanesulfonate (MMS) resistance and PCNA unloading (Figures 1B and 1C, 216–791)—despite its importance for mediating interaction with SUMOylated proteins (Parnas et al, 2011). This observation that MMS sensitivity generally mirrors failure of PCNA unloading led us to design further experiments aimed at examining whether PCNA hyper-accumulation on DNA is the major cause of the MMS sensitivity and other defects observed in an elg1D mutant

Summary

Introduction

Maintenance of the genome is crucial for all living organisms since loss of genome stability leads to mutations and chromosome rearrangements, causing cancers and other life-threatening diseases (Aguilera and Gomez-Gonzalez, 2008; Negrini et al, 2010). Loss of factors involved in these processes generally causes profound genome instability (Mailand et al, 2013; Negrini et al, 2010). Loss of the ELG1 gene causes gross chromosomal rearrangements, increased sister chromatid recombination, defective sister chromatid cohesion, derailed telomere length maintenance, and sensitivity to the DNA alkylating drug methyl methanesulfonate (MMS) (Banerjee and Myung, 2004; Bellaoui et al, 2003; Ben-Aroya et al, 2003; Kanellis et al, 2003; Maradeo and Skibbens, 2009; Parnas et al, 2009; Smolikov et al, 2004). The mechanism by which Elg ensures genome integrity is unknown

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