12 Genetic Approaches to Translation Initiation in Saccharomyces cerevisiae

Abstract

Historically, biochemistry has been the main approach for studying the eukaryotic translation initiation process, with most effort directed toward mammalian systems from which the factorology of translation initiation became well developed. Less than 15 years ago, little was known of the factorology of the yeast system, let alone whether a similar mechanism for initiating protein synthesis existed. At that time, the genetics of yeast began to prove itself as an effective approach to study the mechanism of eukaryotic translation. The similarities between the mammalian and yeast initiation processes, now well established, enable us to assess the mechanism of initiation by combining biochemical and genetic data, a very powerful means to dissect the eukaryotic translation machinery. The ability to do genetics provides additional dimensions to the analysis of translation initiation. As discussed below, it affords direct selection for suppressor mutations in genes that encode factors. These suppressor genes help to define those factors that function at particular steps in the initiation pathway and to show how individual subunits contribute to the activity of multisubunit initiation factors. This has always been one of the rate-limiting problems associated with the biochemical analysis of translation initiation, because the complexity of the process was not compatible, in many cases, with developing specific assays for factors or subunits of factors at defined steps in the pathway. Genetic suppressor analysis can also be a very sensitive method for detecting factor function. It has the potential to define new factors, which may not be realized by biochemical approaches,...