CANDIDA-ALBICANS ALS3 AND INSIGHTS INTO THE NATURE OF THE ALS GENE FAMILY

The ALS1 (agglutinin-like sequence) gene of Candida albicans encodes a protein similar to alpha-agglutinin, a cell-surface adhesion glycopro tein of Saccharomyces cerevisiae (Hoyer et al. 1995). A central domain of a tandemly repeated 108-bp sequence is found in the ALS1 coding re gion. This tandem-repeat motif hybridizes to multiple C. albicans geno mic DNA fragments, indicating the possibility of other ALS1-like genes in C. albicans (Hoyer et al. 1995). To determine if these fragments c onstitute a gene family, tandem-repeat-hybridizing genomic fragments w ere isolated from a fosmid library by PCR screening using primers base d on the consensus tandem-repeat sequence of ALS1 (Hoyer et al. 1995). One group of fosmids, designated ALS3, encodes a gene with 81% identi ty to ALS1. The sequences of ALS1 and ALS3 are most conserved in the t andem-repeat domain and in the region 5' of the tandem repeats, Northe rn-blot analysis using unique probes from the 3' end of each gene demo nstrated that ALS1 expression varies, depending on which C. albicans s train is examined, and that,ALS3 is hyphal-specific. Both genes are fo und in a variety of C. albicans and C. stellatoidea strains examined. The predicted Als1p and Als3p exhibit features suggesting that both ar e cell-surface glycoproteins. Southern blots probed with conserved seq uences from the region 5' of the tandem repeats suggest that other ALS -like sequences are present in the C. albicans genome and that the ALS family may be larger than originally estimated.