FACT Assists Base Excision Repair by Boosting the Remodeling Activity of RSC.

John Lalith Charles Richard,Elsa Ben Simon,Ali Hamiche,Imtiaz Nisar Lone,Stefan Dimitrov,Christophe Papin,Manu Shubhdarshan Shukla,Dimitar Angelov,Yohan Roulland,Hervé Menoni,Khalid Ouararhni,Tapas Kundu

doi:10.1371/journal.pgen.1006221

Abstract

FACT, in addition to its role in transcription, is likely implicated in both transcription-coupled nucleotide excision repair and DNA double strand break repair. Here, we present evidence that FACT could be directly involved in Base Excision Repair and elucidate the chromatin remodeling mechanisms of FACT during BER. We found that, upon oxidative stress, FACT is released from transcription related protein complexes to get associated with repair proteins and chromatin remodelers from the SWI/SNF family. We also showed the rapid recruitment of FACT to the site of damage, coincident with the glycosylase OGG1, upon the local generation of oxidized DNA. Interestingly, FACT facilitates uracil-DNA glycosylase in the removal of uracil from nucleosomal DNA thanks to an enhancement in the remodeling activity of RSC. This discloses a novel property of FACT wherein it has a co-remodeling activity and strongly enhances the remodeling capacity of the chromatin remodelers. Altogether, our data suggest that FACT may acts in concert with RSC to facilitate excision of DNA lesions during the initial step of BER.

Highlights

DNA is packaged under the form of chromatin in the eukaryotic nucleus
Some available data indicate that FACT, in addition to transcription, is involved, as mentioned above, in both transcription-coupled nucleotide excision repair (TC-NER) and DNA double strand break (DSB) repair [35,36,37,38]
To test if FACT is recruited at Base Excision Repair (BER)-lesions we used HeLa cells transiently expressing fluorescently labeled FACT, i.e. a fusion of DsRed with SSRP1 (DsRed-SSRP1), the smaller subunit of FACT

Summary

Introduction

DNA is packaged under the form of chromatin in the eukaryotic nucleus. The nucleosome, the repeating unit of chromatin, consists of an octamer of core histones (two each of H2A, H2B, H3 and H4), around which DNA is wrapped in two superhelical turns [1]. Each core histone contains a structured domain, the histone fold, and an unstructured NH2-terminus [2,3,4]. Both the linker histone and the NH2-termini of core histones are involved in the assembly and maintenance of the 30 nm chromatin [5,6,7] fiber and the mitotic chromosome [8,9]. The chromatin remodeler RSC belongs to the SWI/SNF family and it is involved in the repair of damaged DNA [21,22]. We have recently analyzed the mechanism of RSC-induced nucleosome mobilization and have shown that RSC generates initially an ensemble of particles with highly altered histone-DNA interactions, which are further mobilized by RSC [24]

Methods

Results

Conclusion