Elements involved in @entity26 regulation of the @entity375 XXXX gene.

@entity55607 @entity375 @entity26 @entity43541
The @entity55607 gene of @entity375 encodes the minor species, iso-2, of the cytochrome c protein. Its expression is governed by two regulatory sequences upstream from the gene: a positive site which stimulates transcription 240 base pairs 5' from the protein-coding sequence (-240) and a negative site which inhibits transcription at -300. In this study, the nature of the positive site and its relationship to the negative site has been investigated. Expression of the @entity55607 gene is weakly inducible by @entity26 . This effect was greatly enhanced by the semidominant @entity43541 -16 mutation in the trans-acting gene @entity43541 . The weak @entity26 regulation in wild-type cells and the enhanced induction in @entity43541 -16 mutants were found to be mediated through the positive site. A mutational analysis of this site implicated at least part of a tandem, direct repeat of 9 base pairs as essential for the functioning of this site. The relationship between the positive and negative sites was investigated by comparing the expression of the intact gene with that of derivatives lacking either one or the other site. The expression of the gene containing only the negative site was actually stimulated anaerobically, while the gene containing the positive site alone, although having higher expression aerobically than anaerobically, had higher anaerobic expression than did the intact gene. Thus, it appeared that the combination of the positive and negative sites suppressed anaerobic expression. A model which attempts to explain these properties of the two sites and account for the regulation of the expression of the intact gene is presented.
