The zinc cluster proteins U pc2 and E cm22 promote filamentation in S accharomyces cerevisiae by sterol biosynthesis‐dependent and ‐independent pathways

The transition between a unicellular yeast form to multicellular filaments is crucial for budding yeast foraging and the pathogenesis of many fungal pathogens such as C andida albicans . Here, we examine the role of the related transcription factors E cm22 and U pc2 in S accharomyces cerevisiae filamentation. Overexpression of either ECM 22 or UPC 2 leads to increased filamentation, whereas cells lacking both ECM 22 and UPC 2 do not exhibit filamentous growth. E cm22 and U pc2 positively control the expression of FHN 1 , NPR 1 , PRR 2 and sterol biosynthesis genes. These genes all play a positive role in filamentous growth, and their expression is upregulated during filamentation in an E cm22/ U pc2‐dependent manner. Furthermore, ergosterol content increases during filamentous growth. UPC 2 expression also increases during filamentation and is inhibited by the transcription factors S ut1 and S ut2. The expression of SUT 1 and SUT 2 in turn is under negative control of the transcription factor Ste12. We suggest that during filamentation S te12 becomes activated and reduces SUT 1 / SUT 2 expression levels. This would result in increased UPC 2 levels and as a consequence to transcriptional activation of FHN 1 , NPR 1 , PRR 2 and sterol biosynthesis genes. Higher ergosterol levels in combination with the proteins F hn1, N pr1 and P rr2 would then mediate the transition to filamentous growth.