Short- and long-range interactions in the HIV-1 5′ UTR regulate genome dimerization and packaging

RNA dimerization is the noncovalent association of two human immunodeficiency virus-1 (HIV-1) genomes. It is a conserved step in the HIV-1 life cycle and assumed to be a prerequisite for binding to the viral structural protein Pr55Gag during genome packaging. Here, we developed functional analysis of RNA structure-sequencing (FARS-seq) to comprehensively identify sequences and structures within the HIV-1 5′ untranslated region (UTR) that regulate this critical step. Using FARS-seq, we found nucleotides important for dimerization throughout the HIV-1 5′ UTR and identified distinct structural conformations in monomeric and dimeric RNA. In the dimeric RNA, key functional domains, such as stem-loop 1 (SL1), polyadenylation signal (polyA) and primer binding site (PBS), folded into independent structural motifs. In the monomeric RNA, SL1 was reconfigured into long- and short-range base pairings with polyA and PBS, respectively. We show that these interactions disrupt genome packaging, and additionally show that the PBS–SL1 interaction unexpectedly couples the PBS with dimerization and Pr55Gag binding. Altogether, our data provide insights into late stages of HIV-1 life cycle and a mechanistic explanation for the link between RNA dimerization and packaging.Peer Reviewe

RNA Structures and Their Role in Selective Genome Packaging.

To generate infectious viral particles, viruses must specifically select their genomic RNA from milieu that contains a complex mixture of cellular or non-genomic viral RNAs. In this review, we focus on the role of viral encoded RNA structures in genome packaging. We first discuss how packaging signals are constructed from local and long-range base pairings within viral genomes, as well as inter-molecular interactions between viral and host RNAs. Then, how genome packaging is regulated by the biophysical properties of RNA. Finally, we examine the impact of RNA packaging signals on viral evolution

Isolation and characterization of bacteriophages from India, with lytic activity against Mycobacterium tuberculosis.

Bacteriophages are being considered as a promising natural resource for the development of alternative strategies against mycobacterial diseases, especially in the context of the wide spread occurrence of drug-resistance amongst the clinical isolates of M. tuberculosis. However, there isnâ t much information documented on mycobacteriophages from India. Here, we report the isolation of 17 mycobacteriophages using M. smegmatis as the bacterial host where 9 phages also lyse M. tuberculosis H37Rv. We present detailed analysis of one of these mycobacteriophage (PDRPv). TEM and PCR analysis (of a conserved region within the TMP gene) shows PDRPv to belong to Siphoviridae family and B1 sub-cluster, respectively. The genome (69110 bp) of PDRPv is circularly permuted double-stranded DNA with ~66% GC content and has 106 open reading frames (ORFs). On the basis of sequence similarity and conserved domains, we have assigned function to 28 ORFs and have broadly categorized them into six groups that are related to replication genome maintenance, DNA packaging, virion release, structural proteins, lysogeny related genes and endolysins. The present study reports the occurrence of novel anti-mycobacterial phages in India and highlights their potential to contribute to our understanding of these phages and their gene products as potential antimicrobial agents.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author