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Regulación de la expresión génica mediada por el tallo ribosómico de Saccharomyces cerevisiae

Autor Revuelta-Cervantes, Jesús
DirectorRemacha, Miguel
Palabras clave Saccharomyces cerevisiae
Fecha de publicación 2008
EditorUniversidad Autónoma de Madrid
ResumenThe stalk is an essential, evolutionary conserved and very dynamic structure located in the ribosomal large subunit at the entrance of the peptidic tunnel. The ribosomal stalk of Saccharomyces cerevisiae is composed of four acid phosphoproteins (P1α, P1β, P2α, P2β) with an average molecular weight of 11 kDa, that form a pentamer along with another protein called P0, larger (33.7 kDa) and essential for cell viability. The stalk is involved in interactions between ribosomes and soluble translational factors. No further functions are known, except that the pattern of expressed proteins varies depending on differences in its protein composition. It is possible that these differences in protein expression pattern were caused by one or more affected transcriptional or translational regulator/s. Following this way, in the present Thesis, hibridization to microarrays technology and other approaches were employed in order to take evidence about this putative regulation mechanism over mRNAs translation. Increasing in number of mRNAs molecules associated to translational activated ribosomes, founded in polirribosomal structures, in mutant strains was looked for. In other words, we were looking for genes better transcribed in mutant or in wild type (those worse transcribed in mutant) that change their behaviour in translation. In fact, only a little number of genes seemed to show differences in their expression status between transcription and translation (i.e. Overexpressed genes in transcription in the mutant that not appeared overexpressed in translation in wild type, or viceversa). In deed, data obtained employing different microarray platforms and methodologies were unable to yield the desired result because techniques fail in sensitivity. However, I have found out effects in the regulation of phosphate and methionine metabolism pathways as well as in the expression of a set of apparently disjointed genes involved in gene expression regulation, transport, mitochondrial and response to stress, as more representative of those sets. In this way, both metabolism pathways were found downregulated else their own regulators in the mutant, while transporters, response to stress, and mitochondrial-related genes appeared spreaded by all clasiffication clusters. Actually, these groups of genes are not isolated, existing functional connections beetwen them: genes which respond to stress, regulate transcription by binding to DNA and they are located in mitochondria; or genes associated to mitochondria and involved in thermal stress response by affecting tRNA maduration. Other experiments showed results that allowed us to unveil any kind of involvement of the acid proteins in the mechanisms of ribosomal subunits joining and their biosynthesis, by unbalancing the 60S/40S ratio in mutants which were defective in the whole or a subset of these four acid proteins. This should occur at different level depending on stalk composition of those strains. These unexpected results point towards possible effects or regulation mecanism of acid phosphoproteins in the ribosomal stalk over the own ribosomal assembly and subunit interactions that had not been previously described
Descripción Tesis doctoral inédita leida en la Universidad Autónoma. Facultad de Ciencias. Departamento de Biología Molecular. Fecha de lectura: 15-02-2008
URI http://hdl.handle.net/10261/8375
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