SMARCAL1 maintains telomere integrity during DNA replication

Proc Natl Acad Sci U S A. 2015 Dec 1;112(48):14864-9. doi: 10.1073/pnas.1510750112. Epub 2015 Nov 17.

Abstract

The SMARCAL1 (SWI/SNF related, matrix-associated, actin-dependent, regulator of chromatin, subfamily A-like 1) DNA translocase is one of several related enzymes, including ZRANB3 (zinc finger, RAN-binding domain containing 3) and HLTF (helicase-like transcription factor), that are recruited to stalled replication forks to promote repair and restart replication. These enzymes can perform similar biochemical reactions such as fork reversal; however, genetic studies indicate they must have unique cellular activities. Here, we present data showing that SMARCAL1 has an important function at telomeres, which present an endogenous source of replication stress. SMARCAL1-deficient cells accumulate telomere-associated DNA damage and have greatly elevated levels of extrachromosomal telomere DNA (C-circles). Although these telomere phenotypes are often found in tumor cells using the alternative lengthening of telomeres (ALT) pathway for telomere elongation, SMARCAL1 deficiency does not yield other ALT phenotypes such as elevated telomere recombination. The activity of SMARCAL1 at telomeres can be separated from its genome-maintenance activity in bulk chromosomal replication because it does not require interaction with replication protein A. Finally, this telomere-maintenance function is not shared by ZRANB3 or HLTF. Our results provide the first identification, to our knowledge, of an endogenous source of replication stress that requires SMARCAL1 for resolution and define differences between members of this class of replication fork-repair enzymes.

Keywords: SMARCAL1; c-circle; replication stress; telomere.

Publication types

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

MeSH terms

  • Animals
  • Chromosomes, Human / genetics
  • Chromosomes, Human / metabolism*
  • DNA Damage / physiology
  • DNA Helicases / genetics
  • DNA Helicases / metabolism*
  • DNA Replication / physiology*
  • HeLa Cells
  • Humans
  • Mice
  • Recombination, Genetic / physiology
  • Telomere / genetics
  • Telomere / metabolism*
  • Telomere Homeostasis / physiology*

Substances

  • SMARCAL1 protein, human
  • Smarcal1 protein, mouse
  • DNA Helicases
  • ZRANB3 protein, human