Histone H2AX phosphorylation in response to changes in chromatin structure induced by altered osmolarity.
DNA strand breaks trigger marked phosphorylation of histone H2AX (i.e. gamma-H2AX). While DNA double-strand breaks (DSBs) provide a strong stimulus for this event, the accompanying structural alterations in chromatin may represent the actual signal that elicits gamma-H2AX. Our data show that changes in chromatin structure are sufficient to elicit extensive gamma-H2AX formation in the relative absence of DNA strand breaks. Cells subjected to hypotonic (0.05 M) treatment exhibit gamma-H2AX levels that are equivalent to those found after the induction of 80-200 DNA DSBs (i.e. 2-5 Gy). Despite this significant increase in phosphorylation, cell survival remains relatively unaffected (<10% cytotoxicity), and there is no significant increase in apoptosis. Nuclear staining profiles indicate that gamma-H2AX-positive cells induced under altered tonicity exhibit variable levels of staining, ranging from uniform pan staining to discrete punctate foci more characteristic of DNA strand breakage. The capability to induce significant gamma-H2AX formation under altered tonicity in the relative absence of DNA strand breaks suggests that this histone modification evolved in response to changes in chromatin structure.
Baure
Jennifer
J
Department of Neurological Surgery, University of California, San Francisco, CA 94110, USA.
Izadi
Atefeh
A
Suarez
Vannina
V
Giedzinski
Erich
E
Cleaver
James E
JE
Fike
John R
JR
Limoli
Charles L
CL
D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002531:Cerebellum / Q000166:cytology; D002843:Chromatin / Q000378:metabolism*; D005434:Flow Cytometry; D006657:Histones / Q000378:metabolism*; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology; D007150:Immunohistochemistry; D051379:Mice; D009994:Osmolar Concentration; D010766:Phosphorylation / Q000187:drug effects; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
D002843:Chromatin; C468783:H2AX protein, human; D006657:Histones; D007038:Hypotonic Solutions; C475961:gamma-H2AX protein, mouse