Differential Transcription of the Fibroin and Sericin-1 Genes in Cell-Free Extracts

Devices of the extraction procedues and a recovery of the final supernatant as tiers accompanied with a transcription ability assessment of the individual tiers have enabled us to develop a variety of cell-free transcription systems. The latter step revealed that the factors necessary for faithful transcription as well as enhanced transcription form aggregates or complexes indicating an intrinsic nature of these factors to interact each other. Altogether 14 cell-free transcription systems have been developed from Bombyx mori embryos and tissues of various developmental stages and a cultured cell line, and screened for activities enhancing the basal promoter levels of the silk genes. Using these extracts a differential transcription of plural tissue-specific genes was tried. The fibroin gene was preferentially transcribed than the sericin-1 gene in the extracts from the posterior silk glands where the fibroin gene is specifically transcribed in vivo, while the sericin-1 gene was dominant to the fibroin gene in the extracts from the middle silk glands where the sericin-1 gene is specifically transcribed. Thus, these nuclear extracts offer us a biochemical clue assaying factors responsible for the differential transcription.