Werner helicase is localized to transcriptionally active nucleoli of cycling cells

Exp Cell Res. 1998 Aug 1;242(2):487-94. doi: 10.1006/excr.1998.4124.


Mutations at the Werner helicase locus (WRN) are responsible for the Werner syndrome (WS), a "caricature of aging." We have localized the Werner protein (WRNp) to the nucleoli of replicating mammalian cells, where its appearance is associated with transcriptional activity. A dramatic reduction of the nucleolar signal and of [3H]uridine incorporation occurred when cultures were made quiescent or were exposed to 4-nitroquinoline-1-oxide (4NQO), to which WS cells are particularly susceptible. Total cellular levels of WRNp, however, did not change, and virtually all WRNp was in the nuclear fractions, consistent with translocation to the nucleoplasm and/or masking of the epitopes. The 4NQO-induced altered state of WRNp was prevented by Na3VO4, but not by okadaic acid, suggesting that WRNp localization/function is partially regulated by kinases/phosphatases for Tyr substrates on WRNp or interacting proteins. The repression of rDNA transcription by 4NQO was not reversed by Na3VO4. We suggest that physiological states and genotoxic agents modulate the interaction of WRNp with rDNA, consistent with a role of WRNp in rDNA transcription.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 4-Nitroquinoline-1-oxide / pharmacology
  • Animals
  • COS Cells / cytology
  • COS Cells / drug effects
  • COS Cells / enzymology
  • Carcinogens / pharmacology
  • Cell Cycle / genetics
  • Cell Line, Transformed
  • Cell Nucleolus / drug effects
  • Cell Nucleolus / enzymology*
  • Cell Nucleolus / genetics
  • Culture Media, Serum-Free / pharmacology
  • DNA Helicases / analysis
  • DNA Helicases / drug effects
  • DNA Helicases / genetics
  • DNA Helicases / metabolism*
  • DNA, Ribosomal / drug effects
  • DNA, Ribosomal / genetics
  • Enzyme Inhibitors / pharmacology
  • Exodeoxyribonucleases
  • Fluorescent Antibody Technique, Indirect
  • Humans
  • Phosphoric Monoester Hydrolases / antagonists & inhibitors
  • RecQ Helicases
  • Staining and Labeling
  • Transcription, Genetic / genetics
  • Tumor Cells, Cultured / cytology
  • Tumor Cells, Cultured / drug effects
  • Tumor Cells, Cultured / enzymology
  • Werner Syndrome / enzymology*
  • Werner Syndrome / genetics
  • Werner Syndrome Helicase


  • Carcinogens
  • Culture Media, Serum-Free
  • DNA, Ribosomal
  • Enzyme Inhibitors
  • 4-Nitroquinoline-1-oxide
  • Exodeoxyribonucleases
  • Phosphoric Monoester Hydrolases
  • DNA Helicases
  • RecQ Helicases
  • WRN protein, human
  • Werner Syndrome Helicase