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Regulation of HIV-1 transcription by RBF-1 and RBF-2

University of British Columbia

Lentiviruses, including human immunodeficiency virus type 1 (HIV-1), characteristically form latent integrated proviruses whose transcription can be induced by extracellular signals. The level of HIV-1 gene expression is determined by the 5' long terminal repeat (LTR), which directs the host cell RNA polymerase II machinery to synthesize viral transcripts. The HIV-1 LTR responds to multiple signals, including the protein-tyrosine kinase (PTK)/Ras/Raf signaling pathway. Downstream nuclear targets of PTK/Ras/Raf are of interest because this pathway is implicated in the development of human tumors. This thesis describes experiments designed to determine the czs-acting sequences of the HIV-1 LTR that are necessary for Ras-responsiveness and to characterize the cellular transcription factors that bind to them. Data presented in this thesis demonstrate that Ras-responsive HIV-1 transcription requires two previously undescribed factors, RBF-1 and RBF-2. RBF-1 binds to Ets-like motifs located between nucleotides -151 and -142, and within the NF-kB binding sites. RBF-2 binds the HIV-1 LTR at nucleotides -131 to -121 and immediately 3' of the TATA box. RBF-1, or associated proteins, are phosphorylated in response to the activation of a PTK, v-fps. Moreover, RBF-1 contains the Ets family member GABPα, and an interacting protein, GABPβ₁. RBF-1 and RBF-2 appear to share similar DNA binding subunits of apparent molecular weight 100 K. Mutation of the RBF-1 and RBF-2 binding elements (RBEs) prevents Ras stimulation of HIV LTR-directed transcription. These data define a mechanism for Ras responsiveness of HIV-l transcription that requires GABP, as a component of RBF-1, and the previously uncharacterized cellular transcription factor, RBF-2.

Thesis/Dissertation

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2009-04-01

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http://hdl.handle.net/2429/6724

Biochemistry and Molecular Biology

University of British Columbia

UBCV

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