Tariq M. Rana

TAT-ASSOCIATED KINASE (P-TEFB) : A COMPONENT OF TRANSCRIPTION PREINITIATION AND ELONGATION COMPLEXES

Human immunodeficiency virus, type 1 (HIV-1) Tat protein activates transcription from the HIV-1 long terminal repeat. Tat interacts with TFIIH and Tat-associated kinase (a transcription elongation factor P-TEFb) and requires the carboxyl-terminal domain of the largest subunit of RNA polymerase II (pol II) for transactivation. We developed a stepwise RNA pol II walking approach and used Western blotting to determine the role of TFIIH and P-TEFb in HIV-1 transcription elongation. Our results demonstrate the new findings that P-TEFb is a component of the preinitiation complex and travels with the elongating RNA pol II, whereas TFIIH is released from the elongation complexes before the trans-activation responsive region RNA is synthesized. Our results suggest that TFIIH and P-TEFb are involved in the clearance of promoter-proximal pausing of RNA pol II on the HIV-1 long terminal repeat at different stages.

Synthesis of a metal-ligating amino acid suitable for solid phase assembly of peptides

Abstract The synthesis of an amino acid analog, N-α-Fmoc-N-e-Tetrabutyl EDTA-L-Lysine, suitable for incorporating a strong metal binding site at any internal sequence position in a peptide is described.

Selection of HIV replication inhibitors: Chemistry and biology

Publisher Summary There is a great need to find new drugs and treatment strategies. Available HIV drugs inhibit two key enzymes of the virus, reverse transcriptase and protease. Given the pathogenesis of HIV mutants capable of resisting triple-drug therapies, the identification of drugs that target HIV proteins, other than reverse transcriptase and protease, is a high priority for the development of new drugs. HIV-1 is a complex retrovirus that encodes six regulatory proteins, including Tat and Rev, essential for viral replication. Inhibition of Tat and Rev function provides attractive targets for new antiviral therapies. The Tat protein is a potent transcriptional activator of the HIV-1 long terminal repeat promoter element. A regulatory element between +1 and +60 in the HIV-1 long terminal repeat, which is capable of forming a stable stem-loop structure designated trans-activation responsive (TAR), is critical for Tat function. The Tat protein functions as a transcriptional activator, whereas Rev acts as a sequence-specific nuclear RNA export factor. Rev is involved in efficient nuclear export, and hence expression of the various incompletely spliced viral transcripts. The target RNA sequence required for Rev function is called the Rev response element (RRE) and is located within the env reading flame. Additional screening of microbial fermentation extracts was carried out to identify more potent Rev—RRE binding inhibitors. An extract of the fungal solid fermentation culture of Epicoccum nigrum WC47880 was found to inhibit the binding of Rev—RRE. The axis contains two positively acting elements, the Rev protein and its RNA target sequence, the RRE. Scattered throughout the HIV genome in the genes coding for virion structural proteins are CRSs (constitutive repressor sequences) that act in cis to constitutively down-regulate the expression of the messenger RNAs (mRNAs) that contain them. Rev binds to the RRE as a multimer. Evidence indicates that the Rev protein, through its nuclear export signal (NES), binds exportin/CRM1 and Ran guanosine triphosphate (GTP) cooperatively when it is bound to the RRE-containing RNA.