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Human immunodeficiency virus type 1 Tat prevents dephosphorylation of Sp1 by TCF-4 in astrocytes

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Bibliographische Detailangaben
Zeitschriftentitel: Journal of General Virology
Personen und Körperschaften: Rossi, Andrea, Mukerjee, Ruma, Ferrante, Pasquale, Khalili, Kamel, Amini, Shohreh, Sawaya, Bassel E.
In: Journal of General Virology, 87, 2006, 6, S. 1613-1623
Format: E-Article
Sprache: Englisch
veröffentlicht:
Microbiology Society
Schlagwörter:
Virology
Details
Zusammenfassung: <jats:p>Previous examination of the effect of TCF-4 on transcription of the human immunodeficiency virus type 1 (HIV-1) promoter in human astrocytic cells found that TCF-4 affects the HIV-1 promoter through the GC-rich domain (nt −80 to nt −68). Here, the physical interaction and a functional consequence of TCF4–Sp1 contact were characterized. It was shown that expression of TCF-4 in U-87 MG (human astrocytic) cells decreased basal and Sp1-mediated transcription of the HIV-1 promoter. Results from a GST pull-down assay, as well as combined immunoprecipitation and Western blot analysis of protein extracts from U-87 MG cells, revealed an interaction of Sp1 with TCF-4. Using <jats:italic>in vitro</jats:italic> protein chromatography, the region of Sp1 that contacts TCF-4 was mapped to aa 266–350. It was also found that, in cell-free extracts, TCF-4 prevented dsDNA-dependent protein kinase (DNA-PK)-mediated Sp1 phosphorylation. Surprisingly, TCF-4 failed to decrease Sp1-mediated transcription of the HIV-1 long terminal repeat (LTR) and Sp1 phosphorylation in cells expressing HIV-1 Tat. Results from immunoprecipitation/Western blotting demonstrated that TCF-4 lost its ability to interact with Sp1, but not with Tat, in Tat-transfected cells. 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. Interactions among TCF-4, Sp1 and/or Tat may determine the level of viral gene transcription in human astrocytic cells.</jats:p>
Umfang: 1613-1623
ISSN: 0022-1317
1465-2099
DOI: 10.1099/vir.0.81691-0