Investigating the mechanism of translational stimulation by Deleted in Azoospermia-like

Abstract

The proper expression of a gene to a protein is a complicated process with many steps. One of the major steps is translation, the process of decoding a messenger RNA signal and the building of a protein from its component parts. The control of translation is one of the major steps for the overall control of gene expression and its dysregulation is associated with a wide variety of human diseases including neurological, metabolic and reproductive disorders. Dazl family proteins are germ cell restricted RNA binding proteins that contain a motif characteristic of this family, the DAZ domain. Whilst humans encode all three family members DAZ, DAZL and BOULE, flies only possess the boule gene. The members of this family have an essential conserved role in gametogenesis in a wide variety of organisms from worm to man with loss of function resulting in phenotypes ranging from male or female infertility or both. However, little is known about the molecular role of these proteins in germ cell development. A previous study within the laboratory showed that several vertebrate Dazl family members can stimulate translation of a reporter gene in Xenopus laevis oocytes, suggesting a conserved role in mRNA specific translational control. This is consistent with studies in invertebrates. It was proposed that Dazl proteins fulfil this function through an interaction with a translation initiation factor, poly(A) binding protein, PABP. The aim of this thesis was to further refine this model of action. The work presented here investigates several fundamental questions regarding the mechanism of Dazl-mediated stimulation. First, it investigated the step of translation initiation that Dazl acts upon and explored the initiation factors that may be required. Second, it addressed in more detail the requirements for an interaction between Dazl and the poly(A) binding protein, PABP. Third, it examined the potential role of another factor, DAZ associated protein 1, DAZAP1, in Dazl-mediated stimulation. The role of multi-protein complexes containing Dazl bound to the 3’UTR that localise, repress and stimulate translation of specific mRNAs at defined times during gametogenesis are discussed.