INVITRO TRANSLATION OF EPIDERMAL RNA FROM DIFFERENT ANATOMICAL REGIONS AND METAMORPHIC STAGES OF HYALOPHORA-CECROPIA

Epidermal RNA isolated from different anatomical regions and metamorphic stages of Hyalophora cecropia was translated in vitro with commercial wheat germ and rabbit reticulocyte systems. The translation products were analyzed by 2D gel electrophoresis. The two systems yielded identical products if canine microsomal membranes were added to remove signal peptides from the reticulocyte products. The endogenous processing by the wheat germ extract occurred even in the presence of protease inhibitors. Some of the processed translation products co-migrated with unlabeled cuticular protein standards. All of the major cuticular proteins could be identified, but only when translations were carried out with RNA from epidermis underlying cuticle containing these proteins. Hence, cuticular protein distribution is due to differential synthesis and not to differential extractability. For larval abdominal RNA, most of the major translation products did not co-migrate with known larval cuticular proteins or with proteins synthesized and retained by the epidermis. These unknown products were lower in apparent molecular weight than the cuticular proteins. Their identity remains unknown; they may be premature translation products, but altering translation conditions did not reduce their abundance. © 1990.