Double Monoubiquitination Modifies the Molecular Recognition Properties of p15PAF Promoting Binding to the Reader Module of Dnmt1

Amaia González-Magaña, Alain Ibáñez de Opakua, Nekane Merino, Hugo Monteiro, Tammo Diercks, Javier Murciano-Calles, Irene Luque, Pau Bernadó, Tiago N Cordeiro, Alfredo De Biasio, Francisco J Blanco

Research output: Contribution to journalArticle

Abstract

The proliferating cell nuclear antigen (PCNA)-associated factor p15PAF is a nuclear protein that acts as a regulator of DNA repair during DNA replication. The p15PAF gene is overexpressed in several types of human cancer, and its function is regulated by monoubiquitination of two lysines (K15 and K24) at the protein N-terminal region. We have previously shown that p15PAF is an intrinsically disordered protein which partially folds upon binding to PCNA and independently contacts DNA through its N-terminal tail. Here we present an NMR conformational characterization of p15PAF monoubiquitinated at both K15 and K24 via a disulfide bridge mimicking the isopeptide bond. We show that doubly monoubiquitinated p15PAF is monomeric, intrinsically disordered, and binds to PCNA as nonubiquitinated p15PAF does but interacts with DNA with reduced affinity. Our SAXS-derived conformational ensemble of doubly monoubiquitinated p15PAF shows that the ubiquitin moieties, separated by eight disordered residues, form transient dimers because of the high local effective ubiquitin concentration. This observation and the sequence similarity with histone H3 N-terminal tail suggest that doubly monoubiquitinated p15PAF is a binding target of DNA methyl transferase Dnmt1, as confirmed by calorimetry. Therefore, doubly monoubiquitinated p15PAF directly interacts with PCNA and recruits Dnmt1 for maintenance of DNA methylation during replication.

Original languageEnglish
Pages (from-to)2315-2326
Number of pages12
JournalACS Chemical Biology
Volume14
Issue number10
DOIs
Publication statusPublished - 18 Oct 2019

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