Stable maintenance of the Mre11-Rad50-Nbs1 complex is sufficient to restore the DNA double-strand break response in cells lacking RecQL4 helicase activity.

Abstract

The proper cellular response to DNA double-strand breaks (DSBs) is critical for maintaining the integrity of the genome. RecQL4, a DNA helicase of which mutations are associated with Rothmund-Thomson syndrome (RTS), is required for the DNA DSB response. However, the mechanism by which RecQL4 performs these essential roles in the DSB response remains unknown. Here, we show that RecQL4 and its helicase activity are required for maintaining the stability of the Mre11-Rad50-Nbs1 (MRN) complex on DSB sites during a DSB response. We found using immunocytochemistry and live-cell imaging that the MRN complex is prematurely disassembled from DSB sites in a manner dependent upon Skp2-mediated ubiquitination of Nbs1 in RecQL4-defective cells. This early disassembly of the MRN complex could be prevented by altering the ubiquitination site of Nbs1 or by expressing a deubiquitinase, Usp28, which sufficiently restored homologous recombination repair and ATM, a major checkpoint kinase against DNA DSBs, activation abilities in RTS, and RecQL4-depleted cells. These results suggest that the essential role of RecQL4 in the DSB response is to maintain the stability of the MRN complex on DSB sites and that defects in the DSB response in cells of patients with RTS can be recovered by controlling the stability of the MRN complex.

• Authors: Hyunsup Kim, Hyemin Choi, Jun-Sub Im, Soon-Young Park, Gwangsu Shin, Jung-Ho Yoo, Gyungmin Kim, Joon-Kyu Lee
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 297 Issue 4 Pg. 101148 (10 2021) ISSN: 1083-351X [Electronic] United States
• PMID: 34473993 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.

Chemical References

• Cell Cycle Proteins
• DNA-Binding Proteins
• MRE11 protein, human
• Multiprotein Complexes
• NBN protein, human
• Nuclear Proteins
• MRE11 Homologue Protein
• Acid Anhydride Hydrolases
• Rad50 protein, human
• RECQL4 protein, human
• RecQ Helicases

Topics

• Acid Anhydride Hydrolases (genetics, metabolism)
• Cell Cycle Proteins (genetics, metabolism)
• Cell Line, Tumor
• DNA Breaks, Double-Stranded
• DNA Repair
• DNA-Binding Proteins (genetics, metabolism)
• HEK293 Cells
• Humans
• MRE11 Homologue Protein (genetics, metabolism)
• Multiprotein Complexes (genetics, metabolism)
• Nuclear Proteins (genetics, metabolism)
• RecQ Helicases (genetics, metabolism)