Pol eta is required for DNA replication during nucleotide deprivation by hydroxyurea.
Hydroxyurea reduces DNA replication by nucleotide deprivation, whereas UV damage generates DNA photoproducts that directly block replication fork progression. We show that the low fidelity class Y polymerase Pol eta is recruited to proliferating cell nuclear antigen at replication forks both by hydroxyurea and UV light. Under nucleotide deprivation, Pol eta allows cells to accumulate at the G1/S boundary by facilitating slow S-phase progression and promotes apoptosis. Normal cells consequently enter apoptosis at a faster rate than Pol eta-deficient cells. Coincident with hydroxyurea-induced S-phase delay, Pol eta-deficient cells undergo more replication fork breakage and accumulate more foci of the Mre11/Rad50/Nbs1 complex and phosphorylated histone H2AX. We conclude that under conditions of nucleotide deprivation, Pol eta is required for S-phase progression but is proapoptotic. However, as Pol eta is reported to require higher nucleotide concentrations than class B replicative polymerases, its recruitment by hydroxyurea requires it to function under suboptimal conditions. Our results suggest that hydroxyurea-induced apoptosis occurs at the G1/S boundary and that initiation of the S-phase requires greater nucleotide concentrations than does S-phase progression.
de Feraudy
S
S
Auerback Melanoma Laboratory, UCSF Cancer Center, University of California, San Francisco, CA, USA.
Limoli
C L
CL
Giedzinski
E
E
Karentz
D
D
Marti
T M
TM
Feeney
L
L
Cleaver
J E
JE
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000502:physiology* / Q000528:radiation effects; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured / Q000201:enzymology / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication / Q000187:drug effects*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000502:physiology*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006657:Histones; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology*; D000076228:MRE11 Homologue Protein; D009711:Nucleotides / Q000378:metabolism*; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011995:Recombination, Genetic; D016196:S Phase / Q000502:physiology* / Q000528:radiation effects; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum; D000099270:Y-Family DNA Polymerases
D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D004259:DNA-Directed DNA Polymerase; D006657:Histones; D006918:Hydroxyurea; D000076228:MRE11 Homologue Protein; D009711:Nucleotides; D018809:Proliferating Cell Nuclear Antigen; C468783:H2AX protein, human; C121766:MRE11 protein, human; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases