The dynamic, co-ordinated remodelling of the actin cytoskeleton is attributed to the interaction of actin with a wide variety of actin regulating proteins. The remodelling of actin is central to many cellular processes including endocytic uptake, polarisation of growth, cell motility, and is important for the ability of cells to respond to many intracellular and extracellular signals. Therefore, the study of individual actin regulating proteins enables a greater understanding of the complex overall control of the actin network and many cellular processes. Sla1p is an endocytic adaptor protein with several known roles in the cytoplasm, which include linking proteins involved in the early stages of endocytic uptake with those required for the actin polymerisation at endocytic sites. The data presented in this thesis however details the nuclear localisation of Sla1p. In addition to this initial observation, further analysis has allowed the proposal of a mechanism for the nuclear translocation of Sla1p. This was achieved by analysis of potential nuclear transport signals in wild-type and sla1 mutants, consideration of phosphorylatory mechanisms, and by detailed studies of nuclear transport receptor mutants. Finally, results of microarray analysis undertaken between wild-type and sla1 mutant strains were used to elucidate potential roles of nuclear Sla1p. These studies suggest that Sla1p localises both to the cytoplasm and the nucleus in S. cerevisiae and that its activity and cellular localisation may be regulated primarily through phosphorylation. The key to the dynamic remodelling of the actin cytoskeleton is the coordinated control of filament nucleation, polymerisation and disassembly. Data presented in this thesis demonstrates the association of the cortical patch protein Ysc84p with actin filaments, and the ability of Ysc84p to both sever and cap these filaments in vitro. A possible regulatory mechanism for the protein is also considered. Additionally, a Ysc84p homologue is localised to dynamic actin structures in mammalian cells and studies suggest that this protein may have a similar actin regulatory mechanism. These studies therefore suggest an exciting role for the cortical patch protein Ysc84p in the regulated control of branched actin filaments in S. cerevisiae.