The Prr1 response regulator is essential for transcription of ste11(+) andfor sexual development in fission yeast

Schizosaccharomyces pombe expresses a putative transcription factor, named Prr1, which is intriguing in the sense that it contains a bacterial type of phospho-accepting receiver domain, preceded by a mammalian heat shock fact or (HSF2)-like DNA-binding domain. The receiver domain is most probably inv olved in an as yet unidentified histidine-to-aspartate (His-to-Asp) phospho relay pathway ill S. pombe. In this study, the structure, function, and cel lular localization of Prr1 were assessed in the context of oxidative stress and Histo-Asp phosphorelay. As the most intriguing result of this study, w e found that Prr1 is essential not only for the expression of genes induced by oxidative stress (e.g., ctt1(+) and trr1(+)), but also for the expressi on of ste11(+) which in turn is responsible for the expression of a variety of genes required for sexual development. Accordingly, Prr1-deficient cell s are not only hypersensitive to oxidative stress, but also severely defect ive in conjugation and/or spore formation. These results suggested that the transcription factor Prr1 plays a pivotal role in an as yet unknown signal transduction pathway that is implicated in sexual differentiation. These f indings are discussed with special reference to the well-characterized tran scription factors Pap1 and Atf1 of S. pombe.