Posttranscriptional regulation of specific protein synthesis in the silkmoth wing, as revealed by actinomycin D

Abstract

The synthesis of both total and electrophoretically fractionated proteins was studied in the wing epidermis of developing silkmoths, using a simple organ culture system which maintains the cells in synthetically normal condition for approximately 2 days. Differences were detected in the electrophoretic profile of proteins synthesized at different developmental stages, and correlated with transition from growth-related to differentiation-related products. Actinomycin D induced an apparently exponential decay in incorporation into total protein; the half-life of the decay ranged from 10 to 13 hr, depending on the stage of development. Double-label experiments indicated that decay of protein synthesis in the presence of actinomycin is not uniform, but proceeds at different rates for different components. Putative differentiation-specific products may be associated with differential resistance to actinomycin. At a specific developmental stage, actinomycin induced a transient secondary stimulation of overall incorporation. Measurements of leucine specific activity suggested that protein synthesis (rather than merely incorporation) is affected, and that “superinduction” is not limited to a few protein species.