Nuclear colocalization of cellular and viral myc proteins with HSP70 in myc-overexpressing cells

P J Koskinen, L Sistonen, G Evan, R Morimoto, K Alitalo

Research output: Contribution to journalArticleScientificpeer-review

Abstract

The c-myc oncogene and its viral counterpart v-myc encode phosphoproteins which have been located within cell nuclei, excluding nucleoli. We have expressed the c-myc gene under the simian virus 40 early promoter and studied the distribution of its protein product in transient expression assays in COS, HeLa, and 293 cells. We found three distinct patterns of c-myc immunofluorescence in the transfected cells: one-third of the c-myc-positive cells displayed a diffuse nuclear distribution, and in two-thirds of the cells the c-myc fluorescence was accumulated either in small amorphous or in large multilobed phase-dense nuclear structures. Unexpectedly, these structures also stained for the HSP70 heat shock protein in both heat-shocked and untreated cells. Our results indicate that both transient and stable overexpression of either the c-myc or v-myc protein induces translocation of the endogenous HSP70 protein from the cytoplasm to the nucleus, where it becomes sequestered in structures containing the myc protein. Interestingly, the closely related N-myc protein does not stimulate substantial nuclear expression of the HSP70 protein. Studies with chimeric myc proteins revealed that polypeptide sequences encoded by the second exon of c-myc are involved in colocalization with HSP70.

Original languageEnglish
Pages (from-to)842-51
Number of pages10
JournalJournal of Virology
Volume65
Issue number2
DOIs
Publication statusPublished - Feb 1991
MoE publication typeA1 Journal article-refereed

Keywords

  • Animals
  • Antibodies
  • Avian Sarcoma Viruses/genetics
  • Cell Line
  • Cell Nucleus/metabolism
  • Cell Transformation, Neoplastic
  • Fluorescent Antibody Technique
  • Genes, myc
  • Genetic Vectors
  • HeLa Cells/metabolism
  • Heat-Shock Proteins/analysis
  • Hot Temperature
  • Humans
  • Proto-Oncogene Proteins c-myc/analysis
  • Quail
  • Restriction Mapping
  • Transfection

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