The Genetic Profiles of TIF1 and TIF2 Duplicate Genes
As one of the key steps in protein synthesis, translation initiation is subjected to multi-level regulation which is achieved via diverse mechanisms. The cell adjusts protein synthesis accordingly to its status and environment. The degree of contribution of the processes involved in the regulation of translation initiation is still poorly understood. The first part of this study focuses on identifying mechanisms of regulation in a translationally deficient yeast system, impaired by the loss of one or the other of the TIF1/2 duplicate genes, which together code for the eukaryotic initiation factor 4A (eIF4A). A major finding of this research is related to the functional competences associated with the two duplicate members of the gene pair. Although the genetic profile associated with TIF1 highlights a connection with transcriptional process, the majority of transcription-translation inter-talk is allocated with TIF2, along with a dense network of genetic interactions surrounding the SAGA complex. TIF2 is also the only paralog devoted to interactions with a substantial group of functionally related genes involved in early meiotic gene expression. Protein degradation in the global control of protein synthesis represents a fundamental process and accounts for diverse points of control, in particular through ubiquitination/deubiquitination. This research concludes that functional turnover of proteins and the translation/transcription inter-talk emerges as the most significant contributors to the sophistically regulated translational regulation, The second part of this study aims to determine the extent of similarity and divergence between the TIF1 and TIF2 paralogs. Growth of their individual deletion strains was challenged under different chemical and environmental conditions with the intent to explore the relative contributions of each duplicate in response to an extend range of perturbations. The pair of duplicates appeared convincingly robust in coping with these adversities under disparate cellular contexts, thus suggesting a highly conserved and backed-up genetic network. One of the primary treatments made use of lithium, a condition which was hoped to help, along with furthering our understanding of the TIF1 and TIF2 networks, in formulating an explanation on how augmented translation initiation overcomes lithium toxicity. Although this approach did not return results that could be used to address this unresolved topic, evaluation of genetic inhibition and suppression was highly instructive regarding the mechanisms of response triggered upon lithium/galactose stress. Regulation and synchronization of basic cellular processes were affected: emphasis brought on aspects of cell communication highlighted mechanisms articulated by kinase enzymes and the importance of repression of cell cycle progression in control of protein synthesis. Data from the screen also indicated the stress that combined lithium/galactose treatment places on central metabolic pathways, for instance those between the Leloir, gluconeogenesis, and trehalose pathways.