Identification of Elg1 interaction partners and effects on post-replication chromatin re-formation.

Vamsi K Gali,Anne D Donaldson,Yuki Katou,Katsuhiko Shirahige,Tom Owen-Hughes,Takashi Kubota,Katsunori Fujiki,David Dickerson

doi:10.1371/journal.pgen.1007783

Vamsi K Gali, Anne D Donaldson + Show 6 more

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https://doi.org/10.1371/journal.pgen.1007783

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Abstract

Elg1, the major subunit of a Replication Factor C-like complex, is critical to ensure genomic stability during DNA replication, and is implicated in controlling chromatin structure. We investigated the consequences of Elg1 loss for the dynamics of chromatin re-formation following DNA replication. Measurement of Okazaki fragment length and the micrococcal nuclease sensitivity of newly replicated DNA revealed a defect in nucleosome organization in the absence of Elg1. Using a proteomic approach to identify Elg1 binding partners, we discovered that Elg1 interacts with Rtt106, a histone chaperone implicated in replication-coupled nucleosome assembly that also regulates transcription. A central role for Elg1 is the unloading of PCNA from chromatin following DNA replication, so we examined the relative importance of Rtt106 and PCNA unloading for chromatin reassembly following DNA replication. We find that the major cause of the chromatin organization defects of an ELG1 mutant is PCNA retention on DNA following replication, with Rtt106-Elg1 interaction potentially playing a contributory role.

Highlights

The genetic material in eukaryotes is packaged into chromatin, composed mainly of DNA and nucleosomes
DNA replication is the central process that duplicates the genetic information during cell multiplication
Examining causes of the chromatin re-assembly defect, we show that accumulation of PCNA on DNA is the main cause of defective chromatin formation in the absence of Elg1

Summary

Introduction

The genetic material in eukaryotes is packaged into chromatin, composed mainly of DNA and nucleosomes. Once the nascent DNA strands have been synthesized, the nucleosomal structure must be reassembled to restore the chromatin and permit reinstatement of epigenetic information. Various replication-associated factors play a key role in ensuring all the genetic and epigenetic information is efficiently duplicated. A critical component of the replication machinery is PCNA, which serves as the processivity factor for DNA polymerases. Apart from acting as an accessory factor for DNA polymerase, PCNA coordinates replication-associated processes including chromatin re-assembly, cohesion establishment, DNA repair and the damage response [2]. During the initiation of each Okazaki fragment, RFC loads PCNA prior to polymerase δ recruitment. On completion of each Okazaki fragment, PCNA must be unloaded, which requires the Elg RFC-Like Complex Removal of PCNA is important, and PCNA accumulation in the absence of Elg contributes to genomic instability phenotypes such as elongated telomeres, telomeric silencing, chromosomal rearrangements, cohesion defects, and increased sister chromatin recombination [7,8,9,10,11]

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