Function and Regulation of Adhesin Gene Families in Saccharomyces cerevisiae, Candida albicans, and Candida glabrata

In fungi, the cell wall plays a primary role contributing to the structural integrity of the cell; in addition to this structural role, the cell wall is, by definition, the interface between the yeast and the environment. This chapter examines the overlapping and divergent function and regulation of some surface glycoprotein gene families in Saccharomyces cerevisiae and its pathogenic cousins Candida glabrata and Candida albicans. S. cerevisiae, C. albicans, and C. glabrata encode a variety of glycosylphosphatidylinositol-linked cell wall proteins (GPI-CWPs) that play accessory roles, functioning primarily as adhesins, facilitating yeast-yeast interactions or yeast adherence to a variety of surfaces. Analysis of adhesin gene regulation in S. cerevisiae and in Candida species has revealed significant overlap in the signals that induce transcription of these gene families as well as the mechanistic basis for that regulation. Analysis of FLO gene transcription reveals unexpected complexity in chromatin regulation in yeast. While the epigenetic regulation of FLO10 and FLO11 expression appears similar and some key regulators (Sfl1) are shared, the requirement for chromatinmodifying proteins which underlie the silencing mechanism is quite different—Hda1 in the case of FLO11 and Hst1-Hst2 and Sir3 in the case of FLO10. This complexity probably foreshadows similar complexity in the regulation of other fungal adhesin families.