Defining the NSD2 interactome: PARP1 PARylation reduces NSD2 histone methyltransferase activity and impedes chromatin binding

Xiaoxiao Huang,Richard D Leduc,Luca Fornelli,Alissa J Schunter,Richard L Bennett,Neil L Kelleher,Jonathan D Licht

doi:10.1074/jbc.ra118.006159

Abstract

NSD2 is a histone methyltransferase that specifically dimethylates histone H3 lysine 36 (H3K36me2), a modification associated with gene activation. Dramatic overexpression of NSD2 in t(4;14) multiple myeloma (MM) and an activating mutation of NSD2 discovered in acute lymphoblastic leukemia are significantly associated with altered gene activation, transcription, and DNA damage repair. The partner proteins through which NSD2 may influence critical cellular processes remain poorly defined. In this study, we utilized proximity-based labeling (BioID) combined with label-free quantitative MS to identify high confidence NSD2 interacting partners in MM cells. The top 24 proteins identified were involved in maintaining chromatin structure, transcriptional regulation, RNA pre-spliceosome assembly, and DNA damage. Among these, an important DNA damage regulator, poly(ADP-ribose) polymerase 1 (PARP1), was discovered. PARP1 and NSD2 have been found to be recruited to DNA double strand breaks upon damage and H3K36me2 marks are enriched at damage sites. We demonstrate that PARP1 regulates NSD2 via PARylation upon oxidative stress. In vitro assays suggest the PARylation significantly reduces NSD2 histone methyltransferase activity. Furthermore, PARylation of NSD2 inhibits its ability to bind to nucleosomes and further get recruited at NSD2-regulated genes, suggesting PARP1 regulates NSD2 localization and H3K36me2 balance. This work provides clear evidence of cross-talk between PARylation and histone methylation and offers new directions to characterize NSD2 function in DNA damage response, transcriptional regulation, and other pathways.

Highlights

NSD2 is a histone methyltransferase that dimethylates histone H3 lysine 36 (H3K36me2), a modification associated with gene activation
poly(ADP-ribose) polymerase 1 (PARP1) and NSD2 have been found to be recruited to DNA double strand breaks upon damage and H3K36me2 marks are enriched at damage sites
We have identified with high confidence 24 nuclear interacting partners of NSD2 involved in multiple molecular pathways and biological processes including chromatin remodeling, gene expression regulation, DNA damage repair, and RNA splicing

Summary

Introduction

NSD2 is a histone methyltransferase that dimethylates histone H3 lysine 36 (H3K36me2), a modification associated with gene activation. We have identified with high confidence 24 nuclear interacting partners of NSD2 involved in multiple molecular pathways and biological processes including chromatin remodeling, gene expression regulation, DNA damage repair, and RNA splicing. GO analysis of the 24 interacting targets using EnrichR through KEGG pathway 2016 suggested NSD2-binding proteins are highly associated with the base excision repair pathway (Fig. 2D), which is responsible for removing base lesions from the genome throughout the cell cycle.

Results

Conclusion