The Npl3 hnRNP prevents R-loop-mediated transcription-replication conflicts and genome instability
This article is available under a Creative Commons License (Attribution-NonCommercial 3.0 Unported). ; Transcription is a major obstacle for replication fork (RF) progression and a cause of genome instability. Part of this instability is mediated by cotranscriptional R loops, which are believed to increase by suboptimal assembly of the nascent messenger ribonucleoprotein particle (mRNP). However, no clear evidence exists that heterogeneous nuclear RNPs (hnRNPs), the basic mRNP components, prevent R-loop stabilization. Here we show that yeast Npl3, the most abundant RNA-binding hnRNP, prevents R-loop-mediated genome instability. npl3¿ cells show transcription-dependent and R-loop-dependent hyperrecombination and genome-wide replication obstacles as determined by accumulation of the Rrm3 helicase. Such obstacles preferentially occur at long and highly expressed genes, to which Npl3 is preferentially bound in wild-type cells, and are reduced by RNase H1 overexpression. The resulting replication stress confers hypersensitivity to double-strand break-inducing agents. Therefore, our work demonstrates that mRNP factors are critical for genome integrity and opens the option of using them as therapeutic targets in anti-cancer treatment. ; Research was funded by grants from the Spanish Ministry of Economy and Competitiveness (Consolider 2010 CSD2007-0015 to A.A. and S.M., BFU2010-16372 to A.A., and BFU2011-28274 to S.M.), the Junta de Andalucía (CVI4567 to A.A.), and the European Union (FEDER). J.M.S.-P. was the recipient of a JAE predoctoral training grant from the Spanish Research Council (CSIC). A.B.H. was supported by a post-doctoral grant from the Asociación Española Contra el Cáncer (AECC). ; Peer reviewed
