Homologous chromosomes make contact at the sites of double-strand breaks in genes in somatic G0/G1-phase human cells.
Double-strand DNA breaks (DSBs) are continuously induced in cells by endogenously generated free radicals and exogenous genotoxic agents such as ionizing radiation. DSBs activate the kinase activity in sensor proteins such as ATM and DNA-PK, initiating a complex DNA damage response that coordinates various DNA repair pathways to restore genomic integrity. In this study, we report the unexpected finding that homologous chromosomes contact each other at the sites of DSBs induced by either radiation or the endonuclease I-PpoI in human somatic cells. Contact involves short segments of homologous chromosomes and is centered on a DSB in active genes but does not occur at I-PpoI sites in intergenic DNA. I-PpoI-induced contact between homologous genes is abrogated by the transcriptional inhibitors actinomycin D and α-amanitin and requires the kinase activity of ATM but not DNA-PK. Our findings provide documentation of a common transcription-related and ATM kinase-dependent mechanism that induces contact between allelic regions of homologous chromosomes at sites of DSBs in human somatic cells.
Department of Pathology and Laboratory Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA.
Manoj
M
Gandhi
Viktoria N
VN
Evdokimova
Karen
K
T Cuenco
Marina N
MN
Nikiforova
Lindsey M
LM
Kelly
James R
JR
Stringer
Christopher J
CJ
Bakkenist
Yuri E
YE
Nikiforov
D053959:Alpha-Amanitin / Q000494:pharmacology; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000502:physiology; D002478:Cells, Cultured; D002877:Chromosomes, Human; D004249:DNA Damage; D051747:DNA-Activated Protein Kinase / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology; D003609:Dactinomycin / Q000494:pharmacology; D016193:G1 Phase; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011839:Radiation, Ionizing; D016192:Resting Phase, Cell Cycle; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins / Q000502:physiology
D053959:Alpha-Amanitin; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; D003609:Dactinomycin; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase; D017346:Protein Serine-Threonine Kinases