Open AccessThe DNA damage response in DNA-dependent protein kinase-deficient SCID mouse cells: Replication protein A hyperphosphorylation and p53 induction
Author(s) -
Laura M. Fried,
Constantinos Koumenis,
Scott Peterson,
Susannah L. Green,
Pierre van Zijl,
Joan AllalunisTurner,
David J. Chen,
Richard Fishel,
Amato J. Giaccia,
J. Martin Brown,
Cordula U. Kirchgessner
Publication year - 1996
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.93.24.13825
Subject(s) - replication protein a , dna damage , biology , microbiology and biotechnology , dna replication , dna repair , hyperphosphorylation , dna , protein kinase a , phosphorylation , gene , dna binding protein , biochemistry , transcription factor
Severe combined immunodeficient (SCID) mice display an increased sensitivity to ionizing radiation compared with the parental, C.B-17, strain due to a deficiency in DNA double-strand break repair. The catalytic subunit of DNA-dependent protein kinase (DNA-PKCS ) has previously been identified as a strong candidate for the SCID gene. DNA-PK phosphorylates many proteinsin vitro , including p53 and replication protein A (RPA), two proteins involved in the response of cells to DNA damage. To determine whether p53 and RPA are also substrates of DNA-PKin vivo following DNA damage, we compared the response of SCID and MO59J (human DNA-PKcs -deficient glioblastoma) cells with their respective wild-type parents following ionizing radiation. Our findings indicate that (i ) p53 levels are increased in SCID cells following ionizing radiation, and (ii ) RPA p34 is hyperphosphorylated in both SCID cells and MO59J cells following ionizing radiation. The hyperphosphorylation of RPA p34in vivo is concordant with a decrease in the binding of RPA to single-stranded DNA in crude extracts derived from both C.B-17 and SCID cells. These results suggest that DNA-PK is not the only kinase capable of phosphorylating RPA. We conclude that the DNA damage response involving p53 and RPA is not associated with the defect in DNA repair in SCID cells and that the physiological substrate(s) for DNA-PK essential for DNA repair has not yet been identified.