J Virol. 1998 Apr;72(4):2615-29. Unique Identifier : AIDSLINE
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.
*Gene Products, tat/METABOLISM *HIV-1/METABOLISM *Transcription