Elimination of radiation-induced gamma-H2AX foci in mammalian nucleus can occur by histone exchange.
Double-strand breaks in mammalian DNA lead to rapid phosphorylation of C-terminal serines in histone H2AX (gamma-H2AX) and formation of large nuclear gamma-H2AX foci. After DNA repair these foci disappear, but molecular mechanism of elimination of gamma-H2AX foci remains unclear. H2AX protein can be phosphorylated and dephosphorylated in vitro in the absence of chromatin. Here, we compared global exchange of GFP-H2AX with kinetics of formation and elimination of radiation-induced gamma-H2AX foci. Maximal number of gamma-H2AX foci is observed one hour after irradiation, when approximately 20% of GFP-H2AX is exchanged suggesting that formation of the foci mostly occurs by in situ H2AX phosphorylation. However, slow elimination of gamma-H2AX foci is weakly affected by an inhibitor of protein phosphatases calyculin A which is known as an agent suppressing dephosphorylation of gamma-H2AX. This indicates that elimination of gamma-H2AX foci may be independent of dephosphorylation of H2AX which can occur after its removal from the foci by exchange.
Svetlova
Maria
M
Institute of Cytology RAS, St Petersburg, Russia.
Solovjeva
Liudmila
L
Nishi
Kayoko
K
Nazarov
Igor
I
Siino
Joseph
J
Tomilin
Nikolai
N
D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D004247:DNA / Q000235:genetics* / Q000528:radiation effects*; D004249:DNA Damage / Q000502:physiology*; D005347:Fibroblasts / Q000502:physiology* / Q000528:radiation effects*; D006657:Histones / Q000235:genetics* / Q000528:radiation effects*; D014158:Transcription, Genetic / Q000235:genetics
C468783:H2AX protein, human; D006657:Histones; D004247:DNA