LSm1-7 complexes bind to specific sites in viral RNA genomes and regulate their translation and replication.

LSm1-7 complexes promote cellular mRNA degradation, in addition to translation and replication of positive-strand RNA viruses such as the Brome mosaic virus (BMV). Yet, how LSm1-7 complexes act on their targets remains elusive. Here, we report that reconstituted recombinant LSm1-7 complexes directly bind to two distinct RNA-target sequences in the BMV genome, a tRNA-like structure at the 3'-untranslated region and two internal A-rich single-stranded regions. Importantly, in vivo analysis shows that these sequences regulate the translation and replication of the BMV genome. Furthermore, both RNA-target sequences resemble those found for Hfq, the LSm counterpart in bacteria, suggesting conservation through evolution. Our results provide the first evidence that LSm1-7 complexes interact directly with viral RNA genomes and open new perspectives in the understanding of LSm1-7 functions.

Genetic characterization of human immunodeficiency virus type 1 from Beira, Mozambique.

In this report, we examined the genetic diversity of HIV-1 strains circulating in the city of Beira, the second largest metropolitan area in Mozambique. A total of 131 blood samples, collected between August and October 2003 from antiretroviral-naïve individuals, were characterized with a combined approach consisting of heteroduplex mobility assay (HMA) subtyping for gag (n=74) and/or env (n=117) genes, and DNA sequence analysis of proviral env (C2V3C3, n=52), LTR (n=30) and/or pol (n=43) genomic regions. Aside from the identification, by bootscanning analysis, of a viral strain with a C/A1 mosaic C2V3C3 structure, classified as subtype A by env HMA, phylogenetic inference studies of the sequence data demonstrated the circulation of genetically diverse subtype C viruses, predominantly of the R5 type. Inspection of the LTR sequences revealed a pattern of structural and regulatory elements typical of subtype C, with 63.3% of the viruses showing three NF-kappaB binding sites. Analysis of the predicted protease sequences enabled us to detect a single primary mutation (I84V, n=1) associated with resistance to protease inhibitors (PI), while secondary mutations were highly prevalent, some of them in combinations which may confer PI resistance. Although an unexpectedly high rate (11.6%) of reverse transcriptase key mutations (V75A, K103N, Y181C, M184I, or P236L) was detected in the sequences analyzed, our data suggest the non-epidemic circulation of resistant viruses, and the absence of multi-class drug resistant viral strains.