The Caenorhabditis elegans spe-26 gene is necessary to form spermatids and encodes a protein similar to the actin-associated proteins kelch and scruin.

Six independent mutations in the Caenorhabditis elegans spe-26 gene cause sterility in males and hermaphrodites by disrupting spermatogenesis. Spermatocytes in mutants with the most severe alleles fail to complete meiosis and do not form haploid spermatids. Instead, these spermatocytes arrest with missegregated chromosomes and mislocalized actin filaments, endoplasmic reticulum and ribosomes. In spite of this arrest some of the nuclei and the organelles that normally transport sperm-specific components to the spermatid mature as if they were in spermatids. The spe-26 gene is expressed throughout the testis in both spermatogonial cells and spermatocytes. It encodes a 570-amino-acid polypeptide, which contains five tandem repeat motifs, each of approximately 50 amino acids. These repeats are similar in sequence to repeats in the Drosophila kelch protein, in the invertebrate sperm protein scruin that cross-links actin filaments, as well as in the mouse and pox virus proteins. The functional importance of these repeat motifs is shown by the fact that five of the spe-26 mutations are in the tandem repeats, and one of the most severe mutations is a substitution in a highly conserved glycine. These results suggest that spe-26 encodes a cytoskeletal protein, perhaps actin binding, which is necessary to segregate the cellular components that form haploid spermatids.

Cleavage of the cII protein of phage lambda by purified HflA protease: control of the switch between lysis and lysogeny.

The activity of the cII protein of phage lambda is probably the critical controlling factor in the choice of the lytic or lysogenic pathway by an infecting virus. Previous work has established that cII activity is regulated through the turnover of cII protein; the products of the hflA and hflB loci of Escherichia coli are needed for a degradative reaction, and lambda cIII functions in stabilizing cII. By using the cloned hflA locus, we have purified a cII-cleaving enzyme that we term HflA. Purified HflA contains three polypeptides; at least two of the subunits are products of the hflA region, and the third is probably a cleavage product of the larger of these two hflA-encoded polypeptides. The HflA protease activity cleaves cII to small fragments. We conclude that the switch between lambda developmental pathways involves regulated cleavage of cII by the specific protease HflA.