Document Detail

Phosphorylation of the Rex protein of human T-cell leukemia virus type I.
MedLine Citation:
PMID:  1400509     Owner:  NLM     Status:  MEDLINE    
Rex protein, the posttranscriptional regulator of human T-cell leukemia virus type I (HTLV-I), is required for the control of viral structural protein expression and virus replication. Rex is a phosphoprotein found predominantly in the cell nucleolus, whose function is thought to be regulated by its nucleolar localization and phosphorylation. Therefore, we investigated the in vivo phosphorylation of Rex protein in more detail. Phosphorylation of Rex occurred in all HTLV-I-infected cell lines examined in vivo, primarily at serine residues and to a very small extent at threonine residues. Treatment of cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) led to significant but transient enhancement of the incorporation of [32P]orthophosphate into Rex protein. N-terminal truncation of Rex protein abolished TPA-dependent phosphorylation. Chymotryptic digestion of phosphorylated Rex yielded two phosphopeptides. In vivo phosphorylation sites were identified as serine residues 70 and 177 and threonine residue 174. Serine 70 was a TPA-dependent phosphorylation site within a regulatory domain. We have already shown that the protein kinase C inhibitor H-7 (1-(5-isoquinolinylsulfonyl)-2-methylpiperazine) specifically blocked accumulation of viral unspliced gag-pol mRNA. Therefore, the phosphorylation at serine 70 may be involved in the regulation of Rex function in response to extracellular stimuli.
Y Adachi; T D Copeland; C Takahashi; T Nosaka; A Ahmed; S Oroszlan; M Hatanaka
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  267     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1992 Oct 
Date Detail:
Created Date:  1992-11-25     Completed Date:  1992-11-25     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  21977-81     Citation Subset:  IM; X    
Institute for Virus Research, Kyoto University, Japan.
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MeSH Terms
Amino Acid Sequence
Blotting, Western
Cell Line
Chromatography, High Pressure Liquid
Gene Products, rex / genetics,  metabolism*
Human T-lymphotropic virus 1 / metabolism*
Molecular Sequence Data
Peptide Mapping
Phosphates / metabolism
Phosphorylation / drug effects
Protein Kinase C / metabolism
Tetradecanoylphorbol Acetate / pharmacology
Grant Support
Reg. No./Substance:
0/Gene Products, rex; 0/Phosphates; 16561-29-8/Tetradecanoylphorbol Acetate; EC Kinase C

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