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Proc Natl Acad Sci U S A. 2017 Jul 18;114(29):7671-7676. doi: 10.1073/pnas.1620208114. Epub 2017 Jul 3.

MRG15-mediated tethering of PALB2 to unperturbed chromatin protects active genes from genotoxic stress.

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Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, United Kingdom.
Research Center for Epigenetic Disease, Graduate School of Frontier Sciences, The University of Tokyo, Tokyo 113-0032, Japan.
Advanced Proteomics Facility, Department of Biochemisty, University of Oxford, Oxford, OX1 3QU, United Kingdom.
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139-4307.
NTU Institute of Structural Biology, Nanyang Technological University, 636921 Singapore.
Cancer Research UK/Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, OX3 7DQ, United Kingdom.
Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, United Kingdom;


The partner and localiser of BRCA2 (PALB2) plays important roles in the maintenance of genome integrity and protection against cancer. Although PALB2 is commonly described as a repair factor recruited to sites of DNA breaks, recent studies provide evidence that PALB2 also associates with unperturbed chromatin. Here, we investigated the previously poorly described role of chromatin-associated PALB2 in undamaged cells. We found that PALB2 associates with active genes through its major binding partner, MRG15, which recognizes histone H3 trimethylated at lysine 36 (H3K36me3) by the SETD2 methyltransferase. Missense mutations that ablate PALB2 binding to MRG15 confer elevated sensitivity to the topoisomerase inhibitor camptothecin (CPT) and increased levels of aberrant metaphase chromosomes and DNA stress in gene bodies, which were suppressed by preventing DNA replication. Remarkably, the level of PALB2 at genic regions was frequently decreased, rather than increased, upon CPT treatment. We propose that the steady-state presence of PALB2 at active genes, mediated through the SETD2/H3K36me3/MRG15 axis, ensures an immediate response to DNA stress and therefore effective protection of these regions during DNA replication. This study provides a conceptual advance in demonstrating that the constitutive chromatin association of repair factors plays a key role in the maintenance of genome stability and furthers our understanding of why PALB2 defects lead to human genome instability syndromes.


DNA replication; MRG15; PALB2; SETD2; transcription

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