Regulated processing of dec-1 eggshell proteins in Drosophila

Abstract

The Drosophila dec-1 gene encodes multiple products that are necessary for proper eggshell assembly. During stages 9-12 of oogenesis the ovarian follicle cells synthesize three alternatively spliced dec-1 RNAs that encode proteins of 106, 125, and 177 kDa. All three of these primary translation products undergo developmentally regulated posttranslational cleavages. Antibodies to trpE fusion proteins containing different regions of the dec-1 proteins have been used to identify processing intermediates as well as stable derivatives of fc106, fc125, and fc177. fc106, the most abundant product of the locus, is cleaved at its N-terminus, producing an N-terminal 25-kDa derivative and s80, a stage 10 eggshell protein. During late oogenesis N-terminal cleavage of s80 yields a 20-kDa N-terminal derivative and a 60-kDa eggshell protein. fc125, which differs from fc106 by a C-terminal extension, is processed at its N-terminus through a series of transient intermediates to a stable 95-kDa C-terminal derivative in late stage 10 egg chambers. Unlike its s80 counterpart, the 95-kDa derivative is not subjected to later cleavage events. fc177, synthesized during stages 11-12, is cleaved to a stable C-terminal derivative of approximately 85 kDa. Although all of the cleavage sites fall within regions that are common to fc106, fc125, and fc177, each protein follows a different maturation pathway which results in a variety of proteins with distinctive N- and C-termini. Our data suggest that inter- or intramolecular interactions dictated by the C-terminal ends of the molecules determine the pathway followed by each dec-1 protein.