Document Type
Article
Publication Date
1992
Abstract
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.
Recommended Citation
Adachi Y, Copeland TD, Takahshi C, et al. Phosphorylation of the Rex protein of human T-Cell leukemia virus type 1. J. Biol. Chem. 1992;267:21977-21981.
Copyright
American Society for Biochemistry and Molecular Biology
Included in
Amino Acids, Peptides, and Proteins Commons, Biological Phenomena, Cell Phenomena, and Immunity Commons, Genetic Structures Commons, Medical Cell Biology Commons, Virus Diseases Commons
Comments
This research was originally published in Journal of Biological Chemistry, volume 267, in 1992. © the American Society for Biochemistry and Molecular Biology.