THE KNH1 GENE OF SACCHAROMYCES-CEREVISIAE IS A FUNCTIONAL HOMOLOG OF KRE9

The KNH1 gene from Saccharomyces cerevisiae was identified as an open reading frame on the right arm of chromosome IV. The product encoded b y the KNH1 gene, Knh1p, shares 46% overall identity with Kre9p, a prot ein required for cell surface beta 1,6-glucan synthesis. While disrupt ion of the KNH1 locus had no effect on cell growth, killer toxin sensi tivity or beta 1,6-glucan levels, overexpression of KNH1 was found to suppress the severe growth defect of a kre9 Delta mutant and restored the level of alkali-insoluble beta 1,6-glucan to almost wild-type leve ls. Knh1p, like Kre9p, can be found in the extracellular culture mediu m as an O-glycoprotein, with a molecular mass of 45-61 kDa. Disruption of both KNH1 and KRE9 is lethal, and unlike single kre9 Delta mutants , could not be rescued by overproducing SKN7, a putative transcription factor involved in the regulation of extracellular matrix assembly. T ranscription of KNH1 was found to be carbon-source and kre9 Delta depe ndent, but SKN7 independent, suggesting that KNH1 is subject to altern ative transcriptional control. The KNH1 sequence has been deposited in GenBank under Accession Number U31538.