CLONING OF CDNAS FOR THE PRECURSOR PROTEIN OF A LOW-MOLECULAR-WEIGHT SUBUNIT OF THE INNER LAYER OF THE EGG ENVELOPE (CHORION) OF THE FISH ORYZIAS-LATIPES

cDNA clones for L-SF, the precursor of a low-molecular-weight subunit (ZI-3) of the inner layer of the Oryzias latipes egg envelope were iso lated from Lambda ZAP cDNA libraries constructed from the poly(A)(+) R NA of the liver of spawning female fish and estrogen-treated male fish . Among them, a clone, L-SF II, is 1473 bp long and contains an open r eading frame encoding a signal peptide of 19 amino acids and L-SF prot ein of 420 amino acids. L-SF protein seems to be glycosylated, judging from the result of the glycanase digestion. L-SF protein contains a d omain similar to ZP-domains in ZP3 of some mammalian species. Northern blot analysis employing XhoI-SmaI fragments of the cloned cDNA as pro bes revealed that expression of the L-SF gene occurred exclusively in the livers of spawning female fish and estrogen-treated male fish and that there was no mRNA encoding L-SF in the ovary of the spawning fema le fish. (C) 1995 Academic Press, Inc.