THE BLI-4 LOCUS OF CAENORHABDITIS-ELEGANS ENCODES STRUCTURALLY DISTINCT KEX2 SUBTILISIN-LIKE ENDOPROTEASES ESSENTIAL FOR EARLY DEVELOPMENT AND ADULT MORPHOLOGY/

Many secreted proteins are excised from inactive proproteins by cleava ge at pairs of basic residues. Recent studies have identified several serine endoproteases that catalyze this cleavage in the secretory path ways of yeast and metazoans. These enzymes belong to the kex2/subtilis in-like family of proprotein convertases. In this paper we describe th e molecular characterization of the bli-4 gene from Caenorhabditis ele gans, which was shown previously by genetic analysis of lethal mutants to be essential for the normal development of this organism. Sequenci ng of cDNA and genomic clones has revealed that bli-4 encodes gene pro ducts related to the kex2/subtilisin-like family of proprotein convert ases. Analysis of bli-4 cDNAs has predicted four protein products, whi ch we have designated blisterases A,B,C, and D. These protein products share a common amino terminus, but differ at the carboxyl termini, an d are most likely produced from alternatively spliced transcripts. We have determined the molecular lesions for three bli-4 alleles (h199, h 1010, and q508) that result in developmental arrest during late embryo genesis. In each case, the molecular lesions are within exons common t o all of the BLI-4 isoforms. The original defining allele of bli-4, e9 37, is completely viable yet exhibits blistering of the adult cuticle. Molecular analysis of this allele revealed a deletion that removes ex on 13, which is unique to blisterase A. No RNA transcript correspondin g to exon 13 is detectable in the blistered mutants. These findings su ggest that blisterase A is required for the normal function of the adu lt cuticle. The bli-4 gene is a complex locus as evidenced by the char acterization of mutant strains and RNA transcripts. Furthermore, our d ata show that functional redundancy may exist among the various BLI-4 isoforms.