Differential regulation of SAP8 and SAP9, which encode two new members of the secreted aspartic proteinase family in Candida albicans

Abstract

Secreted aspartic proteinases (Saps) contribute to the virulence of Candida albicans in systemic animal models of infection. Seven genes encoding Saps (SAP1-SAP7) have been identified to date but evidence suggested the existence of additional SAP genes. The screening of a C. albicans lambda EMBL3 genomic library for the presence of other SAP genes was undertaken. Two new genes, SAP8 and SAP9, were isolated. The N-terminal amino acid sequence deduced from SAP8 downstream of a Kex2p-like cleavage site corresponds to the N-terminal amino acid sequence of the 41 kDa Sap isolated and characterized previously. SAP8 mRNA was expressed preferentially in yeasts at 25 degrees C after 6 and 9 h growth in BSA-containing medium. SAP9 encodes an aspartic proteinase with a Kex2p-like cleavage site and contains a putative glycophosphatidylinositol-anchor signal at the C-terminus. Although the SAP9 gene product has not yet been isolated from cultures of C. albicans, transcripts of SAP9 were observed preferentially in later growth phases when SAP8 expression had decreased.