Ionizing radiation-induced phosphorylation of RPA p34 is deficient in ataxia telangiectasia and reduced in aged normal fibroblasts.
Replication protein A (RPA, also called human single stranded DNA binding protein, hSSB) is a trimeric, multifunctional protein complex involved in DNA replication, DNA repair and recombination. Phosphorylation of RPA p34 subunit is observed after exposure of cells to radiation and other DNA damaging agents, which implicates the protein not only in repair but also in the regulation of replication on damaged DNA template. Here, we show that the phosphorylation observed in RPA p34 after exposure to ionizing radiation, X- or gamma-rays, is reduced and occurs later in primary fibroblasts from patients suffering from ataxia telangiectasia (AT), as compared to normal fibroblasts. We also show that in primary normal human fibroblasts, radiation-induced phosphorylation of RPA p34 is 'age'-dependent and decreases significantly as cultures senesce. Radiation-induced phosphorylation of RPA p34 is nearly absent in non-cycling cells, while the expression of p21cipl/wafl/sdil remains inducible. The results demonstrate a growth-state and culture-age dependency in radiation-induced RPA p34 phosphorylation, and suggest the operation of a signal transduction pathway that is inactivated in senescing or quiescent fibroblasts and defective in AT cells.
Cheng
X
X
Thomas Jefferson University, Department of Radiation Oncology, Philadelphia, PA 19107, USA.
Cheong
N
N
Wang
Y
Y
Iliakis
G
G
D000375:Aging / Q000378:metabolism*; D001260:Ataxia Telangiectasia / Q000378:metabolism / Q000473:pathology*; D002453:Cell Cycle; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics / Q000528:radiation effects; D004249:DNA Damage; D004265:DNA Helicases / Q000528:radiation effects*; D004260:DNA Repair / Q000528:radiation effects; D004261:DNA Replication / Q000528:radiation effects*; D004277:DNA, Single-Stranded / Q000528:radiation effects*; D004268:DNA-Binding Proteins / Q000528:radiation effects*; D004791:Enzyme Inhibitors / Q000528:radiation effects; D005347:Fibroblasts / Q000378:metabolism / Q000528:radiation effects*; D005720:Gamma Rays; D005786:Gene Expression Regulation / Q000528:radiation effects; D006801:Humans; D010766:Phosphorylation / Q000528:radiation effects; D011995:Recombination, Genetic / Q000528:radiation effects; D051716:Replication Protein A; D015398:Signal Transduction / Q000528:radiation effects; D014965:X-Rays
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C497167:RPA1 protein, human; D051716:Replication Protein A; D004265:DNA Helicases