Analysis of potential phosphorylation sites in human T cell leukemia virus type 1 Tax

Amber Krause Boehm, Judith A. Stawhecker, O. John Semmes, Patrick E. Jankowski, Robert Lewis, Steven H. Hinrichs

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


The human T cell leukemia virus type 1 (HTLV-1) Tax is a phosphoprotein, however, the contribution of phosphorylation to Tax activity is unknown. Previous studies have shown that phosphorylation of Tax occurs on serine residue(s), within one tryptic fragment, in response to 4βphorbol-12β- myristate-13α-acetate, in both mouse and human cells. Studies were conducted in multiple cell lines to identify the specific phosphorylated serines as a prelude to functional analysis. The phosphorylation pattern of Tax was found to be different in 293T and COS-7 cells in comparison with MT-4 and Px-1 cells. However, one tryptic fragment remained consistent in comigration analyses among all cell lines. Using selected Tax serine mutants a tryptic fragment containing a serine at residue 113 believed to be the site of phosphorylation of Tax did not comigrate with the common phosphorylated tryptic fragment. Analysis of selected Tax mutants for ability to trans- activate the cytomegalovirus promoter demonstrated mutation of serine 77 to alanine reduced transactivation by 90% compared to wild-type Tax. However, examination of the phosphorylation pattern of the serine 77 mutant demonstrated that it is not the site of phosphorylation. These studies demonstrate the importance of using relevant cell lines to characterize the role of phosphorylation in protein function.

Original languageEnglish (US)
Pages (from-to)206-212
Number of pages7
JournalJournal of Biomedical Science
Issue number3
StatePublished - 1999


  • Genetics
  • HTLV-1
  • Mutagenesis
  • Phosphorylation
  • Tax
  • Trans- activation
  • Transcription

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Molecular Biology
  • Clinical Biochemistry
  • Cell Biology
  • Biochemistry, medical
  • Pharmacology (medical)


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