RESUMO
Expression of the flagellar genes in Rhodobacter sphaeroides is dependent on one of the four sigma-54 factors present in this bacterium and on the enhancer binding proteins (EBPs) FleQ and FleT. These proteins, in contrast to other well-characterized EBPs, carry out activation as a hetero-oligomeric complex. To further characterize the molecular properties of this complex we mapped the binding sites or upstream activation sequences (UASs) of six different flagellar promoters. In most cases the UASs were identified at approximately 100 bp upstream from the promoter. However, the activity of the divergent promoters flhAp-flgAp, which are separated by only 53 bp, is mainly dependent on a UAS located approximately 200 bp downstream from each promoter. Interestingly, a significant amount of activation mediated by the upstream or contralateral UAS was also detected, suggesting that the architecture of this region is important for the correct regulation of these promoters. Sequence analysis of the regions carrying the potential FleQ/FleT binding sites revealed a conserved motif. In vivo footprinting experiments with the motAp promoter allowed us to identify a protected region that overlaps with this motif. These results allow us to propose a consensus sequence that represents the binding site of the FleQ/FleT activating complex.
Assuntos
Proteínas de Bactérias/metabolismo , Flagelos/genética , Regiões Promotoras Genéticas , RNA Polimerase Sigma 54/metabolismo , Rhodobacter sphaeroides/metabolismo , Transativadores/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Sequência de Bases , Sítios de Ligação , Sequência Conservada , Flagelos/química , Flagelos/metabolismo , Dados de Sequência Molecular , Ligação Proteica , RNA Polimerase Sigma 54/genética , Rhodobacter sphaeroides/química , Rhodobacter sphaeroides/genética , Transativadores/química , Transativadores/genética , Ativação TranscricionalRESUMO
Organ transplantation represents one of the medical fields with the largest impact and advances. Liver transplantation constitutes a constant challenge in finding viable options to maintain or recover an adequate function when faced with end-stage liver failure. Critical review of the literature was conducted in specific topics on liver transplantation and development in Mexico. We focused our review on medical and surgical topics such as liver procurement from a related living donor, liver transplantation options for patients with liver cancer, especially hepatocellular carcinoma and cholangiocarcinoma, as well as on cellular and molecular biology aspects, such as xenotransplantation and hepatocyte transplantation.