IDENTIFICATION OF A BOMBYX COLLAGENOUS PROTEIN WITH MULTIPLE SHORT DOMAINS OF GLY-XAA-YAA REPEATS - CDNA CHARACTERIZATION AND REGULATION OFEXPRESSION

Using a differential screening strategy, a 2 kb cDNA was isolated from a differentiating Bombyx mori imaginal vying discs library, The avail able reading frame of 1710 bp specifies a conceptual protein with two distinct regions: a 395 amino acid region corresponding to 105 repetit ions of the Gly-Xaa-Yaa triple-helical forming unit arranged in 9 doma ins of 12-54 residues interspaced by short interruptions of 3-17 resid ues and a C-terminal domain of 175 amino acids devoided of triplets, T hese characteristics suggest that the encoded protein is a new member of the collagen superfamily, the first one characterized in Bombyx. No rthern blots reveal a unique 7.4 kb mRNA in imaginal wing discs, epide rmis and brain, In wing discs, the 7.4 kb transcripts accumulate durin g the last larval moult and the spinning stage, Irt vitro studies reve al that this accumulation is dose dependent and detectable within 1 h in response to 20-hydroxyecdysone which acts without de novo protein s ynthesis, A model of regulation of transcript accumulation with regard s to the hormonal level is proposed. Copyright (C) 1996 Elsevier Scien ce Ltd.