Open AccessAnalysis of Human Syndromes with Disordered Chromatin Reveals the Impact of Heterochromatin on the Efficacy of ATM-Dependent G2/M Checkpoint Arrest
Author(s) -
Holly Brunton,
Aaron A. Goodarzi,
Angela T. Noon,
Amruta Shrikhande,
R. Scott Hansen,
Penny A. Jeggo,
Atsushi Shibata
Publication year - 2011
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.05289-11
Subject(s) - cell cycle checkpoint , heterochromatin , biology , dna damage , g2 m dna damage checkpoint , chromatin , microbiology and biotechnology , dna repair , chek1 , cell cycle , cancer research , apoptosis , genetics , dna
Heterochromatin (HC) poses a barrier to γH2AX focus expansion and DNA double-strand break (DSB) repair, the latter being relieved by ATM-dependent KAP-1 phosphorylation. Using high-resolution imaging, we show here that the HC superstructure markedly restricts ATM signaling to cell cycle checkpoint proteins. The impact of HC is greater than anticipated from the percentage of HC-DNA and, in distinction to DSB repair, ATM only partly overcomes the constraints posed by HC. Importantly, we examine ATM signaling in human syndromes with disordered HC. After depletion of MeCP2 and DNMT3B, proteins defective in the Rett and immunodeficiency with centromere instability and facial anomalies (ICF) syndromes, respectively, we demonstrate enhanced γH2AX signal expansion at HC-chromocenters in mouse NIH 3T3 cells, which have visible HC-chromocenters. Previous studies have shown that the G2 /M checkpoint is inefficient requiring multiple DSBs to initiate arrest. MeCP2 and DNMT3B depletion leads to hypersensitive radiation-induced G2 /M checkpoint arrest despite normal DSB repair. Cell lines from Rett, ICF, and Hutchinson-Guildford progeria syndrome patients similarly showed hyperactivated ATM signaling and hypersensitive and prolonged G2 /M checkpoint arrest. Collectively, these findings reveal that heterochromatin contributes to the previously described inefficient G2 /M checkpoint arrest and demonstrate how the signaling response can be uncoupled from DSB repair.