Worm Breeder's Gazette 12(3): 34 (June 15, 1992)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

unc 101, A Negative Regulator of the Vulval Induction Pathway, Encodes a Clathrin Adaptor Protein

Junho Lee, Gregg Jongeward, Paul Sternberg

HHMI, Division of Biology, Caltech, Pasadena, CA 91125

unc-101 is a gene required in many different tissues for survival, defecation, development of some neurons, and normal induction of the vulva. While unc-101 mutants do not have any vulval defect, they have an ability to suppress the vulvaless phenotype of some weak alleles of let-23 .They also suppress strong alleles of lin-2 , lin-7 ,and lin-10 .

We cloned the unc-101 gene, and determined the genomic structure and the cDNA sequence. The gene has 7 exons and 6 introns. The cDNA sequence predicts a protein of 422 amino acids. A database search identified a strong homology to the rat AP47 ,the medium chain of Golgi-associated clathrin adaptor protein complex AP- 1. The amino acid sequence identity between unc-101 and AP47 is 79%.

Intensive biochemical studies have been done on the mammalian adaptor protein complexes. The coated pits of the plasma membrane and Golgi consist of clathrin and adaptors interacting with receptors on the membrane. There are two different adaptor protein complexes, AP-1 and AP-2. AP-1 is localized in trans- Golgi network and is involved in protein sorting and regulated exocytosis. AP-2 is localized on the plasma membrane and is involved in endocytosis of receptors. The medium chains of these adaptor complexes, called AP47 and AP50 respectively, show limited homology to each other (40% identity). A C. elegans homolog of the medium chain of AP-2 was identified by the sequencing consortium (WBG vol.12, No.2, p26 ).

Given very high sequence homology to each other, the mammalian and C. elegans homologs may well have a conserved function. There are many possible roles for unc-101 at the subcellular level including: 1) unc-101 might be involved in the retention of let-23 molecules after their biosynthesis. Then unc-101 mutant cells could have more receptors on their surface. 2) unc-101 might be involved in sorting of lysosomal enzymes required for degradation of signal transduction machinery. Then the unc-101 mutant cells could have more signal transduction. In either case, unc-101 should be expressed in the vulval precursor cells. 3) unc-101 might be responsible for the regulated secretion of the signal molecules. Then the unc-101 mutants could have more signal for vulval induction. In this case, unc-101 should be expressed in the anchor cell. 4) unc-101 might be involved in the regulated secretion of negative regulators of vulval differentiation (e.g. proteases required for degredation of extracellular signal). In this case, unc-101 could be expressed in the hyp7 cells.

Literature Cited:

WBG vol.12, No.2, p26