A new member of the hsp90 family of molecular chaperones interacts with the retinoblastoma protein during mitosis and after heat shock

Chi Fen Chen, Yumay Chen, Kang Dai, Phang Lang Chen, Daniel J. Riley, Wen Hwa Lee

Research output: Contribution to journalArticle

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Abstract

A gene encoding a new heat shock protein that may function as a molecular chaperone for the retinoblastoma protein (Rb) was characterized. The cDNA fragment was isolated by using the yeast two-hybrid system and Rb as bait. The open reading frame of the longest cDNA codes for a protein with substantial sequence homology to members of the hsp90 family. Antibodies prepared against fusions between glutathione S-transferase and portions of this new heat shock protein specifically recognized a 75-kDa cellular protein, hereafter designated hsp75, which is expressed ubiquitously and located in the cytoplasm. A unique LxCxE motif in hsp75, but not in other hsp90 family members, appears to be important for binding to the simian virus 40 T-antigen-binding domain of hypophosphorylated Rb, since a single mutation changing the cysteine to methionine abolishes the binding. In mammalian cells, Rb formed complexes with hsp75 under two special physiological conditions: (i) during M phase, when the envelope that separates the nuclear and cytoplasmic compartments broke down, and (ii) after heat shock, when hsp75 moved from its normal cytoplasmic location into the nucleus. In vitro, hsp75 had a biochemical activity to refold denatured Rb into its native conformation. Taken together, these results suggest that Rb may be a physiological substrate for the hsp75 chaperone molecule. The discovery of a heat shock protein that chaperones Rb identifies a mechanism, in addition to phosphorylation, by which Rb is regulated in response to progression of the cell cycle and to external stimuli.

Original languageEnglish (US)
Pages (from-to)4691-4699
Number of pages9
JournalMolecular and Cellular Biology
Volume16
Issue number9
StatePublished - 1996

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Retinoblastoma Protein
Molecular Chaperones
Heat-Shock Proteins
Mitosis
Shock
Hot Temperature
Complementary DNA
Two-Hybrid System Techniques
Simian virus 40
Viral Tumor Antigens
Nuclear Envelope
Sequence Homology
Glutathione Transferase
Methionine
Cell Division
Open Reading Frames
Cysteine
Cell Cycle
Cytoplasm
Proteins

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cell Biology

Cite this

A new member of the hsp90 family of molecular chaperones interacts with the retinoblastoma protein during mitosis and after heat shock. / Chen, Chi Fen; Chen, Yumay; Dai, Kang; Chen, Phang Lang; Riley, Daniel J.; Lee, Wen Hwa.

In: Molecular and Cellular Biology, Vol. 16, No. 9, 1996, p. 4691-4699.

Research output: Contribution to journalArticle

Chen, Chi Fen ; Chen, Yumay ; Dai, Kang ; Chen, Phang Lang ; Riley, Daniel J. ; Lee, Wen Hwa. / A new member of the hsp90 family of molecular chaperones interacts with the retinoblastoma protein during mitosis and after heat shock. In: Molecular and Cellular Biology. 1996 ; Vol. 16, No. 9. pp. 4691-4699.
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