Timeless Maintains Genomic Stability and Suppresses Sister Chromatid Exchange during Unperturbed DNA Replication.
Genome integrity is maintained during DNA replication by coordination of various replisome-regulated processes. Although it is known that Timeless (Tim) is a replisome component that participates in replication checkpoint responses to genotoxic stress, its importance for genome maintenance during normal DNA synthesis has not been reported. Here we demonstrate that Tim reduction leads to genomic instability during unperturbed DNA replication, culminating in increased chromatid breaks and translocations (triradials, quadriradials, and fusions). Tim deficiency led to increased H2AX phosphorylation and Rad51 and Rad52 foci formation selectively during DNA synthesis and caused a 3-4-fold increase in sister chromatid exchange. The sister chromatid exchange events stimulated by Tim reduction were largely mediated via a Brca2/Rad51-dependent mechanism and were additively increased by deletion of the Blm helicase. Therefore, Tim deficiency leads to an increased reliance on homologous recombination for proper continuation of DNA synthesis. Together, these results indicate a pivotal role for Tim in maintaining genome stability throughout normal DNA replication.
Urtishak
Karen A
KA
Abramson Family Cancer Research Institute, Department of Cancer Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA."
Smith
Kevin D
KD
Chanoux
Rebecca A
RA
Greenberg
Roger A
RA
Johnson
F Brad
FB
Brown
Eric J
EJ
D000818:Animals; D024682:BRCA2 Protein / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004249:DNA Damage / Q000502:physiology*; D004261:DNA Replication / Q000502:physiology*; D042822:Genomic Instability / Q000502:physiology*; D006657:Histones / Q000235:genetics / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation / Q000502:physiology; D051135:Rad51 Recombinase / Q000235:genetics / Q000378:metabolism; D051721:Rad52 DNA Repair and Recombination Protein / Q000235:genetics / Q000378:metabolism; D053484:RecQ Helicases / Q000235:genetics / Q000378:metabolism; D012854:Sister Chromatid Exchange / Q000502:physiology*
D024682:BRCA2 Protein; D018797:Cell Cycle Proteins; D006657:Histones; D047908:Intracellular Signaling Peptides and Proteins; D051135:Rad51 Recombinase; D051721:Rad52 DNA Repair and Recombination Protein; D053484:RecQ Helicases; C106711:BRCA2 protein, mouse; C497196:Rad52 protein, mouse; C509770:Timeless protein, mouse; C495154:Rad51 protein, mouse; C097151:Bloom syndrome protein; C475961:gamma-H2AX protein, mouse