The helicase domain and C-terminus of human RecQL4 facilitate replication elongation on DNA templates damaged by ionizing radiation

Carcinogenesis. 2012 Jun;33(6):1203-10. doi: 10.1093/carcin/bgs149. Epub 2012 Apr 16.

Abstract

The vertebrate RECQL4 (RECQ4) gene is thought to be the ortholog of budding yeast SLD2. However, RecQL4 contains within its C-terminus a RecQ-like helicase domain, which is absent in Sld2. We established human pre-B lymphocyte Nalm-6 cells, in which the endogenous RECQL4 gene was homozygously targeted such that the entire C-terminus would not be expressed. The RECQL4(ΔC/ΔC) cells behaved like the parental cells during unperturbed DNA replication or after treatment with agents that induce stalling of DNA replication forks, such as hydroxyurea (HU). However, after exposure to ionizing radiation (IR), the RECQL4(ΔC/ΔC) cells exhibited hypersensitivity, inability to complete S phase and prematurely terminated or paused DNA replication forks. Deletion of BLM, a gene that also encodes a RecQ helicase, had the opposite phenotype; an almost wild-type response to IR, but hypersensitivity to HU. Targeting both RECQL4 and BLM resulted in viable cells, which exhibited mostly additive phenotypes compared with those exhibited by the RECQL4(ΔC/ΔC) and the BLM(-/-) cells. We propose that RecQL4 facilitates DNA replication in cells that have been exposed to IR.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • DNA / radiation effects
  • DNA Damage*
  • DNA Replication*
  • Genomic Instability
  • Humans
  • Hydroxyurea / pharmacology
  • Precursor Cells, B-Lymphoid / cytology
  • Protein Structure, Tertiary
  • Radiation, Ionizing
  • RecQ Helicases / chemistry*
  • RecQ Helicases / genetics*
  • RecQ Helicases / metabolism*

Substances

  • DNA
  • Bloom syndrome protein
  • RECQL4 protein, human
  • RecQ Helicases
  • Hydroxyurea