HMGN1 interacts with PCNA and facilitates its binding to the nucleosomal array

Tuesday, October 25, 2011 — Poster Session II
Noon – 2:00 p.m.	Natcher Conference Center	NCI	EPIGEN/TRANS/CHROM-10

Authors

• Y Postnikov
• T Kurahashi
• M Zhou
• T Veenstra
• M Bustin

Abstract

HMGN proteins is a super-family of nucleosome binding proteins which affect the structure and activity of the chromatin fiber. We systematically examined nuclear binding partners of HMGN1. Analysis of affinity-purified nuclear proteins by mass spectrometry revealed a specific interaction between Proliferating Cell Nuclear Antigen (PCNA) and HMGN1. PCNA is a highly conserved nuclear protein that plays an important regulatory role in multiple cellular processes. In vitro chromatin-binding assays reveal that HMGN1 enhances the binding of PCNA to chromatin fragments but not to isolated core particles. Fluorescence recovering after photobleaching experiments with cells derived from Hmgn1+/+ and Hmgn1-/- mice indicate that HMGN1 enhances the rate of PCNA recruitment to sites of DNA damage. Microscopic analysis of control and DNA-damaged live cells co-expressing cherry-labeled HMGN1 and yellow fluorescent protein-labeled PCNA, indicate that PCNA but not HMGN1, is rapidly recruited to damaged DNA sites. The kinetics of PCNA-chromatin association before and shortly after DNA damage implies a universal role of HMGN as a nuclear factor facilitating the specific factors to bind to nucleosome-sheltered DNA. Our identification of HMGN1 as a specific PCNA-binding protein suggests a novel mechanism whereby HMGN1 modulates cellular processes, specifically by tethering DNA-binding factors to a chromatin.

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