Tissue-specific transcription enhancement of the fibroin gene characterized by cell-free systems.

Six cell-free extracts have been used to characterize the nature of DNA signals and trans-acting factors responsible for the transcription enhancement of the Bombyx mori fibroin gene. The upstream element of the fibroin gene involved in the enhancement can be divided into two regions. The proximal region, -72 to -32, is recognized as a common enhancing signal by all B. mori extracts from the posterior silk gland, the middle silk gland, the ovarian tissue, and an embryonic cell line. It is weakly recognized by an Antheraea silkworm cell line extract but not by a HeLa cell extract. The distal region, -238 to -73, appears to be a tissue-specific enhancing signal that is recognized more effectively by the posterior silk gland extract than by the middle silk gland extract. These observations suggest that the use of these cell-free systems can offer a means for the biochemical characterization of the trans-acting factors involved in the tissue-specific regulation of the fibroin gene.