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Inhibition of Tat transactivation by the RNA polymerase II CTD-phosphatase FCP1
P Licciardo1, G Napolitano, B Majello
1Department of Genetics, Molecular and General Biology, University of Naples Federico II and the International Institute of Genetics and Biophysics, Italy.
Objectives:
To asses the role of the RNAPII carboxy-terminal domain (CTD) phosphatase FCP1 on HIV-1 Tat-mediated transactivation.
Design:
Construction of expression vectors encoding FCP1 phosphatase and analysis of their functions on Tat activity.
Methods:
Basal and Tat-mediated transactivation of HIV-1 long terminal repeat (LTR)-driven transcription was compared, by transient transfections, in the presence of FCP1 phosphatase. Protein interactions were analysed by in vitro binding assays.
Results:
FCP1 specifically and effectively represses Tat transactivation but not HIV-1 LTR-basal transcription. Protein interaction assays demonstrated that FCP1 specifically and directly binds Tat in vitro.
Conclusion:
The specific and efficient inhibitory function of FCP1 highlights the important role of this CTD-phosphatase in Tat-mediated transactivation, and it suggests that FCP1 might represent a specific target for modulation of Tat activity in infected cells.