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Department of Cell Biology Faculty

Photo of Camilo A. Parada, Ph.D.

Camilo A. Parada, Ph.D.

Assistant Professor

Tel: (718) 270-1143 x6359


Control of HIV-1 gene expression

Research Summary

Our goal is to combine in vitro and in vivo studies to gain a better understanding of the nature of the mammalian cellular factors and their mechanisms of action on HIV-1 gene expression. In particular, we are interested in elucidating the role of novel HIV-1-encoded Tat cofactors in the regulation of HIV-1 transcription elongation, re-initiation, and its link to pre-mRNA processing, a process that is critical for HIV-1 gene expression. This study will, eventually, help define novel targets to block HIV-1 replication.

HIV-1 is the causative agent of AIDS and HIV-1 gene expression is essential for viral replication. Our broad research efforts focus on the understanding of the molecular regulatory events that control HIV-1 gene expression. Our specific efforts are aimed at determining the mechanism(s) by which the HIV-1-encoded Tat protein, in conjunction with mammalian host cell transcription factors and RNA polymerase II, enhances transcription elongation, transcription re-initiation, and early mRNA processing from the HIV-1 promoter. Our experimental approach is to use crude cell-free systems and reconstituted transcription systems, with both recombinant and purified transcription factors and RNA Pol II, that can efficiently recapitulate Tat-mediated HIV-1 transcription observed in vivo. We biochemically dissect these transcription systems to purify and clone cDNAs encoding Tat cofactors for structure-function analysesMechanisims by which TAt cofactors mediate Tat-enhanced HIV-1 transcription are examined both in vitro and in vivo.

Using a reconstituted transcription system, we have recently shown that a novel RNA Pol II-containing complex, that is structurally distinct from the RNA Pol II holoenzyme, is required to support Tat-enhanced transcription elongation and transcription re-initiation. We found that this novel RNA Pol II complex contains several transcription elongation factors, mRNA processing activities, and other novel polypeptides, and we are employing both conventional and affinity-chromatography methods to purify, identify and clone the cDNAs of these novel cellular factors. An in vitro transcription system in which the HIV-1 promoter is assembled into chromatin, is also being used to study the synergism of Tat and the Tat-responsive RNA Pol II complex upon transcription through nucleosome. Complex (es) and transcription factors involved in the control of HIV-1 enhancer activity on chromatin templates are of special interest. As such, we have recently identified a chromatin RNA Pol II-containing complex that efficiently supports Tat-stimulated transcription. Characterization of this complex involves identification of known and novel transcription factors and the elucidation of the mechanisms by which they mediate Tat activity in vitro. By employing chromatin immunoprecipitation (ChiP), the localization of upstream activators (e.g., NF-kB, Sp1), coactivators (e.g., SRB/MED), and Tat-responsive RNA Pol II complexes in either transfected or stably integrated HIV-1-reporter gene contrasts are also being examined.

In summary, our experimental approach and analyses will reveal a better understanding of the control of HIV-1 gene expression, and eventually, to help define novel targets to block HIV-1 replication.


Ph.D. (1991, Memorial Sloan-Kettering Cancer Center and Cornell Graduate School of Medical Sciences)


  1. Parada C.A., Yoon J.B., and Roeder R.G. (1995) A novel LBP-1-mediated restriction at the level of elongation in vitro. J. Biol. Chem. 270: 2274-2283
  2. Parada, C.A., and Roeder, R.G. (1996) Enhanced processivity of RNA polymerase II triggered by Tat-induced phosphorylation of its carboxy-terminal domain. Nature 384, 375-378.
  3. Parada, C.A., and Roeder, R.G. (1999) A novel RNA polymerase II-containing complex potentiates Tat-enhanced HIV-1 transcription. EMBO J. 18, 3688-3701.
  4. Parada, C.A. (2003) Spt5/Spt4 (DSIF) Stimulates General RNA Polymerase II Processivity and Transcription Reinitiation: A Key Role For Tat-enhanced HIV-1 Transcription. Submitted
  5. Hidalgo A., Mai, S., Leung, W., and Parada, C.A. (2003) Novel chromatin RNA Pol II-containing complex mediates potent Tat-enhanced HIV-1 transcription. Submitted