Role of human Pso4 in mammalian DNA repair and association with terminal deoxynucleotidyl transferase

doi:10.1073/pnas.1631060100

Role of human Pso4 in mammalian DNA repair and association with terminal deoxynucleotidyl transferase

Kiran N. Mahajan*,† and
Beverly S. Mitchell*,†,‡

^*Lineberger Comprehensive Cancer Center and ^‡Departments of Pharmacology and Medicine, University of North Carolina, Chapel Hill, NC 27599

Edited by James E. Cleaver, University of California, San Francisco, CA, and approved June 16, 2003 (received for review February 21, 2003)

Abstract

Terminal deoxynucleotidyl transferase (TdT; EC 2.7.7.31) adds nucleotides to DNA ends generated during V(D)J recombination that are subsequently processed by proteins involved in general double-strand break (DSB) repair pathways. We report an association between TdT and a 55-kDa protein in lymphoid cells. This protein, identified as hPso4, is a homolog of the protein encoded by the PS04/PRP19 gene in Saccharomyces cerevisiae that has pleiotropic functions in DNA recombination and error-prone repair. Purified hPso4 binds double-stranded DNA in a sequence-nonspecific manner but does not bind single-stranded DNA. hPso4 protein is induced 15- to 30-fold in cells by γ radiation and chemical mutagens but not by UV treatment. Loss of hPso4 expression induced by siRNA results in accumulation of DSBs, apoptosis, and decreased cell survival after DNA damage. We conclude that hPso4 plays a major and previously undefined role in mammalian DNA DSB repair.

Footnotes

↵ † To whom correspondence may be addressed at: Room 22-044, Lineberger Comprehensive Cancer Center, CB#7295, University of North Carolina, Chapel Hill, NC 27599-7295. E-mail: mitchell{at}med.unc.edu or mahajan{at}med.unc.edu.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations: DSB, double-strand break; TdT, terminal deoxynucleotidyl transferase; NHEJ, nonhomologous end joining; DSBR, DSB repair; BRCT, BRCA1 C terminus; His, histidine; siRNA, small interfering RNA; ds, double-stranded; ss, single-stranded.