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J Biol Chem. 2019 Oct 22. pii: jbc.RA119.011077. doi: 10.1074/jbc.RA119.011077. [Epub ahead of print]

The telomere-binding protein Rif2 and ATP-bound Rad50 have opposing roles in the activation of yeast Tel1ATM kinase.

Author information

1
Biochemistry and Molecular Biophysics, Washington University in Sait Louis School of Medicine, United States.
2
Washington Univ. School of Medicine, United States.
3
Biochemistry and Molecular Biophysics, Washington University School of Medicine, United States.
4
Sloan-Kettering Institute, United States.
5
Dept. of Molecular Biology, Sloan-Kettering Institute, United States.
6
Dept. Biochemistry & Molec. Biophysics, Washington Univ. School of Medicine, United States.

Abstract

Saccharomyces cerevisiae Tel1 is the ortholog of human ATM kinase and initiates a cell cycle checkpoint in response to dsDNA breaks (DSBs). Tel1ATM kinase is activated synergistically by naked dsDNA and the Mre11-Rad50-Xrs2NBS1 complex (MRX). A multi-subunit protein complex, which is related to human shelterin, protects telomeres from being recognized as DSBs, thereby preventing a Tel1ATM checkpoint response. However, at very short telomeres, Tel1ATM can be recruited and activated by the MRX complex, resulting in telomere elongation. Conversely, at long telomeres, Rap1-interacting-factor 2 (Rif2) is instrumental in suppressing Tel1 activity. Here, using an in vitro reconstituted Tel1 kinase activation assay, we show that Rif2 inhibits MRX-dependent Tel1 kinase activity. Rif2 discharges the ATP-bound form of Rad50, which is essential for all MRX-dependent activities. This conclusion is further strengthened by experiments with a Rad50 allosteric ATPase mutant that maps outside of the conserved ATP binding pocket. We propose a model in which Rif2 attenuates Tel1 activity at telomeres by acting directly on Rad50 and discharging its activated ATP-bound state, thereby rendering the MRX complex incompetent for Tel1 activation. These findings expand our understanding of the mechanism by which Rif2 controls telomere length.

KEYWORDS:

ATPase; DNA damage response; MRX; Rad50 ATPase; Rif2; Telomere control; ataxia telangiectasia; checkpoint control; double-stranded break; telomere

PMID:
31640985
DOI:
10.1074/jbc.RA119.011077
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