Scaffold attachment factor A (SAF-A) and Ku temporally regulate repair of radiation-induced clustered genome lesions.
Ionizing radiation (IR) induces highly cytotoxic double-strand breaks (DSBs) and also clustered oxidized bases in mammalian genomes. Base excision repair (BER) of bi-stranded oxidized bases could generate additional DSBs as repair intermediates in the vicinity of direct DSBs, leading to loss of DNA fragments. This could be avoided if DSB repair via DNA-PK-mediated nonhomologous end joining (NHEJ) precedes BER initiated by NEIL1 and other DNA glycosylases (DGs). Here we show that DNA-PK subunit Ku inhibits DGs via direct interaction. The scaffold attachment factor (SAF)-A, (also called hnRNP-U), phosphorylated at Ser59 by DNA-PK early after IR treatment, is linked to transient release of chromatin-bound NEIL1, thus preventing BER. SAF-A is subsequently dephosphorylated. Ku inhibition of DGs in vitro is relieved by unphosphorylated SAF-A, but not by the phosphomimetic Asp59 mutant. We thus propose that SAF-A, in concert with Ku, temporally regulates base damage repair in irradiated cell genome.
Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX, USA.|Houston Methodist Neurological Institute, Houston, TX, USA.|Weill Medical College of Cornell University, Ithaca, NY, USA.
Muralidhar L
ML
Hegde
Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX, USA.|Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX , USA.
Arijit
A
Dutta
Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX, USA.
Chunying
C
Yang
Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX , USA.|Center for Animal Sciences, School of Basic and Applied Sciences, Central University of Punjab, Bathinda, Punjab, India.
Anil K
AK
Mantha
Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX, USA.
Pavana M
PM
Hegde
Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX, USA.
Arvind
A
Pandey
Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX, USA.|Weill Medical College of Cornell University, Ithaca, NY, USA.
Shiladitya
S
Sengupta
Department of Biochemistry & Molecular Biology, University of Calgary, Calgary, Canada.
Yaping
Y
Yu
Institut de Pharmacologie et de Biologie Structurale, CNRS, Université de Toulouse-Université Paul Sabatier, Equipe Labellisée Ligue contre le Cancer, Toulouse, France.
Patrick
P
Calsou
UT Southwestern Medical Center, Dallas, TX, USA.
David
D
Chen
Department of Biochemistry & Molecular Biology, University of Calgary, Calgary, Canada.
Susan P
SP
Lees-Miller
Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX, USA.|Weill Medical College of Cornell University, Ithaca, NY, USA.|Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX , USA.
Sankar
S
Mitra
D053903:DNA Breaks, Double-Stranded; D045647:DNA Glycosylases / Q000502:physiology; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000502:physiology; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000502:physiology; D051747:DNA-Activated Protein Kinase / Q000502:physiology; D004268:DNA-Binding Proteins / Q000502:physiology; D057809:HEK293 Cells; D034722:Heterogeneous-Nuclear Ribonucleoprotein U / Q000502:physiology*; D006801:Humans; D000072200:Ku Autoantigen / Q000502:physiology*; D010766:Phosphorylation; D011832:Radiation Injuries / Q000209:etiology*; D011836:Radiation Tolerance
D004268:DNA-Binding Proteins; C000621393:HNRNPU protein, human; D034722:Heterogeneous-Nuclear Ribonucleoprotein U; C508551:NHEJ1 protein, human; D051747:DNA-Activated Protein Kinase; D045647:DNA Glycosylases; C473634:NEIL1 protein, human; D000072200:Ku Autoantigen; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D045643:DNA Repair Enzymes
BER; DNA-PK; DSB repair; Ku; SAF-A/hnRNP-U