Biomedical subjects

Bruno Sargueil

Publications and source records attributed to Bruno Sargueil.

4 recordsLinked to original sources

PubMed2007

Translational control of retroviruses.

All replication-competent retroviruses contain three main reading frames, gag, pol and env, which are used for the synthesis of structural proteins, enzymes and envelope proteins respectively. Complex retroviruses, such as lentiviruses, also code for regulatory and accessory proteins that have essential roles in viral replication. The concerted expression of these genes ensures the efficient polypeptide production required for the assembly and release of new infectious progeny virions. Retroviral protein synthesis takes place in the cytoplasm and depends exclusively on the translational machinery of the host infected cell. Therefore, not surprisingly, retroviruses have developed RNA structures and strategies to promote robust and efficient expression of viral proteins in a competitive cellular environment.

Animals↗

PubMed2005

HIV-2 genomic RNA contains a novel type of IRES located downstream of its initiation codon.

Eukaryotic translation initiation begins with assembly of a 48S ribosomal complex at the 5' cap structure or at an internal ribosomal entry segment (IRES). In both cases, ribosomal positioning at the AUG codon requires a 5' untranslated region upstream from the initiation site. Here, we report that translation of the genomic RNA of human immunodeficiency virus type 2 takes place by attachment of the 48S ribosomal preinitiation complex to the coding region, with no need for an upstream 5' untranslated RNA sequence. This unusual mechanism is mediated by an RNA sequence that has features of an IRES with the unique ability to recruit ribosomes upstream from its core domain. A combination of translation assays and structural studies reveal that sequences located 50 nucleotides downstream of the AUG codon are crucial for IRES activity.

Base Pairing↗

PubMed2004

Selection and evolution of NTP-specific aptamers.

ATP occupies a central position in biology, for it is both an elementary building block of RNA and the most widely used cofactor in all living organisms. For this reason, it has been a recurrent target for in vitro molecular evolution techniques. The exploration of ATP-binding motifs constitutes both an important step in investigating the plausibility of the 'RNA world' hypothesis and a central starting point for the development of new enzymes. To date, only two RNA motifs that bind ATP have been characterized. The first one is targeted to the adenosine moiety, while the second one recognizes the 'Hoogsteen' face of the base. To isolate aptamers that bind ATP in different orientations, we selected RNAs on an affinity resin that presents ATP in three different orientations. We obtained five new motifs that were characterized and subsequently submitted to a secondary selection protocol designed to isolate aptamers specific for cordycepin. Interestingly, all the ATP-binding motifs selected specifically recognize the sugar-phosphate backbone region of the nucleotides. Three of the aptamers show some selectivity for adenine derivatives, while the remainder recognize any of the four nucleotides with similar efficiency. The characteristics of these aptamers are discussed along with implications for in vitro molecular evolution.

Adenosine Triphosphate↗

PubMed2003

In vitro selection of second site revertants analysis of the hairpin ribozyme active site.

We have used in vitro genetics to evaluate the function and interactions of the conserved base G8 in the hairpin ribozyme catalytic RNA. Second site revertant selection for a G8X mutant, where X is any of the other three natural nucleobases, yielded a family of second site suppressors of the G8U mutant, but not of G8C or G8A, indicating that only G and U can be tolerated at position 8 of the ribozyme. This result is consistent with recent observations that point to the functional importance of G8 N-1 in the chemistry of catalysis by this ribozyme reaction. Suppression of the G8U mutation was observed when changes were made directly across loop A from the mutated base at substrate position +2 or positions +2 and +3 in combination. The same changes made in the context of the natural G8 sequence resulted in a very large drop in activity. Thus, the G8U mutation results in a change in specificity of the ribozyme from 5'-N / GUC-3' to 5'-N / GCU-3'. The results presented imply that G8 interacts directly with U+2 during catalysis. We propose that this interaction favors the correct positioning of the catalytic determinants of G8. The implications for the folding of the ribozyme and the catalytic mechanism are discussed.

Base Sequence↗