KAP-1 promotes resection of broken DNA ends not protected by γ-H2AX and 53BP1 in G₁-phase lymphocytes.
The resection of broken DNA ends is required for DNA double-strand break (DSB) repair by homologous recombination (HR) but can inhibit normal repair by nonhomologous end joining (NHEJ), the main DSB repair pathway in G1-phase cells. Antigen receptor gene assembly proceeds through DNA DSB intermediates generated in G1-phase lymphocytes by the RAG endonuclease. These DSBs activate ATM, which phosphorylates H2AX, forming γ-H2AX in flanking chromatin. γ-H2AX prevents CtIP from initiating resection of RAG DSBs. Whether there are additional proteins required to promote resection of these DNA ends is not known. KRAB-associated protein 1 (KAP-1) (TRIM28) is a transcriptional repressor that modulates chromatin structure and has been implicated in the repair of DNA DSBs in heterochromatin. Here, we show that in murine G1-phase lymphocytes, KAP-1 promotes resection of DSBs that are not protected by H2AX and its downstream effector 53BP1. In these murine cells, KAP-1 activity in DNA end resection is attenuated by a single-amino-acid change that reflects a KAP-1 polymorphism between primates and other mammalian species. These findings establish KAP-1 as a component of the machinery that can resect DNA ends in G1-phase cells and suggest that there may be species-specific features to this activity.
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.
Anthony T
AT
Tubbs
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.
Yair
Y
Dorsett
Department of Immunology, Duke University Medical Center, Durham, North Carolina, USA.
Elizabeth
E
Chan
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.
Beth
B
Helmink
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.
Baeck-Seung
BS
Lee
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.
Putzer
P
Hung
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.
Rosmy
R
George
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.
Andrea L
AL
Bredemeyer
Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University, St. Louis, Missouri, USA.
Anuradha
A
Mittal
Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University, St. Louis, Missouri, USA.
Rohit V
RV
Pappu
Department of Radiation Oncology, Harvard Medical School, Boston, Massachusetts, USA.
Dipanjan
D
Chowdhury
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.
Nima
N
Mosammaparast
Department of Immunology, Duke University Medical Center, Durham, North Carolina, USA.
Michael S
MS
Krangel
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA sleckman@immunology.wustl.edu.
Barry P
BP
Sleckman
D000818:Animals; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics; D053903:DNA Breaks, Double-Stranded; D059766:DNA End-Joining Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016193:G1 Phase / Q000235:genetics*; D006570:Heterochromatin / Q000378:metabolism; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008214:Lymphocytes / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D010766:Phosphorylation / Q000235:genetics
D004268:DNA-Binding Proteins; D006570:Heterochromatin; D006657:Histones; D047908:Intracellular Signaling Peptides and Proteins; D004247:DNA