Characterisation
of the Ssn6-Tup1 corepressor in Schizosaccharomyces pombe.
Fredrik Fagerström-Billai, Anthony Wright
Natural Science Department, Sodertorn University / KI, Alfred Nobel Alle 3,
Huddinge, 14152, Sweden (fredrik.fagerstrom-billai@cbt.ki.se)
The Tup1 and Ssn6 proteins form a general co-repressor of transcription that has been widely characterised in budding yeast. The fission yeast Schizosaccharomyces pombe contains homologues of both proteins and their characterization to date suggests that they work by a similar mechanism to the budding yeast counterparts. However, an important difference is that there are two homologues of the budding yeast TUP1, namely tup11+ and tup12+. We have found that tup12 mutants show a severe reduction in growth on high salt media, while tup11 mutants grow normally under the same conditions. The reduced growth seen in tup12 is similar to that seen for the double mutant. The reduced growth phenotype co-segregates with the tup12 defect and can be rescued by expression of tup12+ from a plasmid. We are using DNA microarray analysis of genome wide expression to more completely define the genes regulated by the two Tup proteins. We have also been studying the possibility that tup11+ and tup12+ might function by distinct mechanisms. The proteins can interact together when expressed at normal levels, confirming previous studies with over expressed proteins. Immunofluorescense shows that the two proteins are found all over the nucleus in a largely overlapping pattern. The location patterns might be associated with specific functional roles of the proteins. These studies as well as studies of functional and physical interactions of the Tup proteins with the Ssn6 protein will be presented.