KAP-1 promotes resection of broken DNA ends not protected by γ-H2AX and 53BP1 in G₁-phase lymphocytes

Mol Cell Biol. 2014 Aug;34(15):2811-21. doi: 10.1128/MCB.00441-14. Epub 2014 May 19.

Abstract

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cells, Cultured
  • DNA / genetics
  • DNA Breaks, Double-Stranded
  • DNA End-Joining Repair / genetics*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • G1 Phase / genetics*
  • Heterochromatin / metabolism
  • Histones / genetics
  • Histones / metabolism
  • Humans
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Lymphocytes / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Phosphorylation / genetics

Substances

  • DNA-Binding Proteins
  • Heterochromatin
  • Histones
  • Intracellular Signaling Peptides and Proteins
  • DNA