Modulation of Sp1 phosphorylation by human immunodeficiency virus type 1 Tat

J Virol. 1998 Apr;72(4):2615-29. doi: 10.1128/JVI.72.4.2615-2629.1998.


We previously reported (K. T. Jeang, R. Chun, N. H. Lin, A. Gatignol, C. G. Glabe, and H. Fan, J. Virol. 67: 6224-6233, 1993) that human immunodeficiency virus type 1 (HIV-1) Tat and Sp1 form a protein-protein complex. Here, we have characterized the physical interaction and a functional consequence of Tat-Sp1 contact. Using in vitro protein chromatography, we mapped the region in Tat that contacts Sp1 to amino acids 30 to 55. We found that in cell-free reactions, Tat augmented double-stranded DNA-dependent protein kinase (DNA-PK)-mediated Sp1 phosphorylation in a contact-dependent manner. Tat mutants that do not bind Sp1 failed to influence phosphorylation of the latter. In complementary experiments, we also found that Tat forms protein-protein contacts with DNA-PK. We confirmed that in HeLa and Jurkat cells, Tat expression indeed increased the intracellular amount of phosphorylated Sp1 in a manner consistent with the results of cell-free assays. Furthermore, using two phosphatase inhibitors and a kinase inhibitor, we demonstrated a modulation of reporter gene expression as a consequence of changes in Sp1 phosphorylation. Taken together, these findings suggest that activity at the HIV-1 promoter is influenced by phosphorylation of Sp1 which is affected by Tat and DNA-PK.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Androstadienes / pharmacology
  • Binding Sites
  • Cell Nucleus / metabolism
  • DNA-Activated Protein Kinase
  • DNA-Binding Proteins*
  • Enzyme Inhibitors / pharmacology
  • Gene Expression
  • Gene Products, tat / genetics
  • Gene Products, tat / metabolism*
  • HIV Long Terminal Repeat
  • HIV-1 / metabolism*
  • HeLa Cells
  • Humans
  • Jurkat Cells
  • Marine Toxins
  • Nuclear Proteins
  • Okadaic Acid / pharmacology
  • Oxazoles / pharmacology
  • Phosphoprotein Phosphatases / antagonists & inhibitors
  • Phosphorylation
  • Point Mutation
  • Protein Serine-Threonine Kinases / metabolism
  • Recombinant Fusion Proteins / genetics
  • Serine / genetics
  • Sp1 Transcription Factor / metabolism*
  • Transcription, Genetic
  • Wortmannin
  • tat Gene Products, Human Immunodeficiency Virus


  • Androstadienes
  • DNA-Binding Proteins
  • Enzyme Inhibitors
  • Gene Products, tat
  • Marine Toxins
  • Nuclear Proteins
  • Oxazoles
  • Recombinant Fusion Proteins
  • Sp1 Transcription Factor
  • tat Gene Products, Human Immunodeficiency Virus
  • Okadaic Acid
  • Serine
  • calyculin A
  • DNA-Activated Protein Kinase
  • PRKDC protein, human
  • Protein Serine-Threonine Kinases
  • Phosphoprotein Phosphatases
  • Wortmannin