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Contact Information |
| Office: |
Ross Hall 232 |
| Lab: |
Ross Hall 233-228 |
| Tel: |
(202) 994-2919 |
| Fax: |
(202) 994-8974 |
| E-mail: |
akumar@gwu.edu |
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Research Interests
A: Regulation of Transcriptional Elongation:
Regulation of transcription elongation is a critical process in the control of viral and cellular gene expression. We have studied transactivation of HIV-1 gene expression as an experimental model for a number of years. The overarching hypothesis is that transcriptional elongation is accomplished by precise post-translational modifications (protein phosphorylations and dephosphorylations) of the transcription factors and chromatin remodeling (histone H3 lysine 4 methylations). HIV-1 gene transactivation provides an ideal experimental system to ask the questions since Tat protein is known to stimulate transcription elongation from the viral promoter.
Our recent results show that HIV Tat modifies substrate specificity of CDK9 kinase to regulate transcription elongation and chromatin remodeling of HIV-1 promoter. The Tat-specified kinase activity can be specifically blocked by a CDK inhibitor which could be a potent antiviral drug.
B: Specific Gene Silencing by RNA Interference (RNAi):
Small interfering RNA (siRNA), that are complementary to specific mRNA sequences, act as guide molecules to direct ribonuclease complexes that degrade the target RNA. Thus one can achieve target specific gene silencing, a powerful tool in genetic analysis. RNA interference (RNAi), or post-transcriptional gene silencing (PTGS), was originally described as being initiated by a synthetic dsRNA (complementary to the target mRNA), which is cleaved into small 21bp siRNA by a ribonulease complex called “dicer”. In human cells, although the synthetic siRNA has been successfully used to achieve target specific gene silencing, the benefits of siRNA is short lived. It is important to understand how RNAi is regulated in human cells to understand the genetic regulation of human diseases.
We reasoned that in human cells the dsRNA mediated innate antiviral (interferon) response is a clue to understanding the regulation of RNAi. As proof of principle we developed human cell lines stably expressing a genetic variant of the dsRNA binding protein (NF90ctv), and showed by gene array assays that the cells induced interferon response genes, which in part enables the cells to resist viral replication. Initial studies show that RNAi response is stimulated in cells expressing NF90ctv. These studies are being continued to decipher the mechanism of regulation of RNA interference in human cells, and how the innate antiviral response regulates RNAi.
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Selected Publications :
- Zhou, M., Deng, L., Kashanchi, F., Shatkin, A.J., and Kumar, A. (2003). The Tat/TAR-dependent phosphorylation of RNAP II CTD stimulates co-transcriptional capping of HIV-1 mRNA. Proc. Natl. Acad.Sci.USA Vol.100:12666-12671.
- Zhou, M., Deng, L., Nekhai, S., Kashanchi, F., Brady, J.N., and Kumar, A. (2003). HIV-1 Tat Activation of Transcription elongation Factors is Inhibited by the P-TEFb kinase Inhibitor, Flavopiridol. (2003).(manuscript submitted to Mol. Cell)
- Agbottah, E.T., Traviss, C., Spruill, A., McArdle, J., and Kumar, A. (2003). Inhibition of Reverse Transcription using Nuclear Factor 90(NF90) Targeted to the HIV-1 TAR Structure. J.Biol.Chem.( submitted).
- Amnosova,T., Jerebtsova, M., Beullen, M., Voloshin,Y., Ray, P., Kumar, A., Bollen, M., and Nekhai,S. (2003). Inhibition of HIV-1 Transcription by NIPP1, a Nuclear Regulator ofProtein Phosphotase 1. J.Biol.Chem. J.Biol.Chem. vol.278:32189-32194.
- Pumfery, A., Deng, L., Maddukuri, A., de la Fuente, C., Li, H., Wade, J.D., Lambert, P., Kumar, A., and Kashanchi, F. (2003). Chromatin Remodeling and Modification During HIV-1 Tat-activated Transcription. Current HIV Research vol.1 pp; 261-274.
- Marques,S.M.P., Veyrune,J-L., Shukla,R.R., and Kumar,A. (2003). Restriction of HIV-1 Rev Function in Murine A9 Cells Involves Rev C-Terminal Domain. J.Virol. 77:3084-3090. 2003.
- Washington, Kareem, Ammosova T., Beullens M., Jerebtsova M., Kumar A., Bollen M., and Nekhai S. (2002). Protein Phosphatase-1 Dephosphorylates the C-terminal Domain of RNA Polymerase-II. J. Biol. Chem. Vol. 277(43): 40442-40448.
- Krasnoselskaya-Riz, I., Spruill, A., Chen, Y-W, Schuster, D. Baker,C., Kumar, A. and Stephan, D.A.(2002). Double-stranded RNA Binding Nuclear Factor 90 Activates Transcriptional Program of Antiviral Response. AIDS Research: Human Retroviruses, Vol.18#8 pp.591-604
- Nekhai, S., Zhou, M. Fernandez A., Lane, W.S., Lamb, N.J.C., Brady J., and kumar, A (2002). HIV-I Tat-associated RNA Pol. II CTD-Kinase, CDK-2, Phosphorylates CDK7 and stimulates Tat- mediated transcription. Bioc.J. Vol.364#3. pp.649-657
- Bharucha, D.C., Zhou, M., nekhai, S., Brady, J.N., Shukla, R.R. and Kumar.A (2002). A Protein Phosphatase from Human T-cells Augments Tat-transactivation of the Human Immunodeficiency Virus Type 1, Long Terminal Repeat. Virology vol.296: 6-16
- Tezak, Z., Hoffman,E.P., Lutz,J.L., Fedczyna,T.O., Stephan,D., Bremmer,E., Krasnoselskaya-Riz,I., Kumar,A., and Pachman,L.M., gene Expression Profiling in Children with Untreated Dermatomyositis: A Novel Model of Pathogenesis.(2002). The Journal of Immunology 4155-4163.
- Zhou, M., Nekhai, S. Bharucha, D.D. Kumar, A., Hui, Ge, Price, D.H., J-M Egly, and Brady J. (2001). TFIIH Inhibits CDK9 Phosphorylation during HIV-1 Transcription. J.Biol.Chem.276:44633-44660.
- Kramer, J.H. Murthi, S.B., Wise, R.M., Mak, I. T., Weglicki, W.B. Antioxidant and lysosomotropic properties of acute d -propranolol underlies its cardioprotection of postischemic hearts from moderate iron-overloaded rats. Exp.Biol. Med. 231:473-484, 2006.
- Tejero-Taldo, M.I., Kramer, J.H., Mak, I-Tong, Komarov, A.M., Chmielinska, J.J., Weglicki, W.B. The nerve-heart connection in the pro-oxidant response to Mg-deficiency. Heart FailureReviews. 11:35-44, 2006.
- Mak, I.T., Kramer, J.H., Chmielinska, J.J., Khalid, H., Landgraf, K., Weglicki, W.B. Inhibition of Neutral endopeptidase potentiates neutrophil activation during Mg-deficiency in the rat. Inflamm. Res. 2008. In Press.
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