TY - JOUR
T1 - Homologous recombination and nonhomologous end-joining repair pathways regulate fragile site stability
AU - Schwartz, Michal
AU - Zlotorynski, Eitan
AU - Goldberg, Michal
AU - Ozeri, Efrat
AU - Rahat, Ayelet
AU - Le Sage, Carlos
AU - Chen, Benjamin P.C.
AU - Chen, David J.
AU - Agami, Reuven
AU - Kerem, Batsheva
PY - 2005/11/15
Y1 - 2005/11/15
N2 - Common fragile sites are specific loci that form gaps and constrictions on metaphase chromosomes exposed to replication stress, which slows DNA replication. These sites have a role in chromosomal rearrangements in tumors; however, the molecular mechanism of their expression is unclear. Here we show that replication stress leads to focus formation of Rad51 and phosphorylated DNA-PKcs, key components of the homologous recombination (HR) and nonhomologous end-joining (NHEJ), double-strand break (DSB) repair pathways, respectively. Down-regulation of Rad51, DNA-PKcs, or Ligase IV, an additional component of the NHEJ repair pathway, leads to a significant increase in fragile site expression under replication stress. Replication stress also results in focus formation of the DSB markers, MDC1 and γH2AX. These foci colocalized with those of Rad51 and phospho-DNA-PKcs. Furthermore, γH2AX and phospho-DNA-PKcs foci were localized at expressed fragile sites on metaphase chromosomes. These findings suggest that DSBs are formed at common fragile sites as a result of replication perturbation. The repair of these breaks by both HR and NHEJ pathways is essential for chromosomal stability at these sites.
AB - Common fragile sites are specific loci that form gaps and constrictions on metaphase chromosomes exposed to replication stress, which slows DNA replication. These sites have a role in chromosomal rearrangements in tumors; however, the molecular mechanism of their expression is unclear. Here we show that replication stress leads to focus formation of Rad51 and phosphorylated DNA-PKcs, key components of the homologous recombination (HR) and nonhomologous end-joining (NHEJ), double-strand break (DSB) repair pathways, respectively. Down-regulation of Rad51, DNA-PKcs, or Ligase IV, an additional component of the NHEJ repair pathway, leads to a significant increase in fragile site expression under replication stress. Replication stress also results in focus formation of the DSB markers, MDC1 and γH2AX. These foci colocalized with those of Rad51 and phospho-DNA-PKcs. Furthermore, γH2AX and phospho-DNA-PKcs foci were localized at expressed fragile sites on metaphase chromosomes. These findings suggest that DSBs are formed at common fragile sites as a result of replication perturbation. The repair of these breaks by both HR and NHEJ pathways is essential for chromosomal stability at these sites.
KW - Common fragile sites
KW - Double-strand breaks
KW - Genomic instability
KW - Homologous recombination
KW - Nonhomologous end-joining
KW - Replication stress
UR - http://www.scopus.com/inward/record.url?scp=27744496209&partnerID=8YFLogxK
U2 - 10.1101/gad.340905
DO - 10.1101/gad.340905
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C2 - 16291645
AN - SCOPUS:27744496209
SN - 0890-9369
VL - 19
SP - 2715
EP - 2726
JO - Genes and Development
JF - Genes and Development
IS - 22
ER -