Cis-acting and trans-acting regulatory mutations define two types of promoters controlled by the qa-1F gene of Neurospora

Abstract

The function of the qa-1F positive regulatory gene of Neurospora has been studied by mapping the initiation sites for transcription of the clustered qa structural genes in wild type, in qa-1F mutants, and in cis-acting activator protein-independent mutants of qa-2 (qa-2ai mutants). Each structural gene under qa-1F control has two to four promoters. The qa-2ai mutations, which include point mutations and small (68-84 bp) duplications 5' to qa-2, allow qa-1F-independent transcription from surrounding qa promoters independently of the orientations and positions (up-stream or downstream) of teh mutations relative to the promoters. However, one subset of promoters was not reactivated by the enhancer-like elements created by these mutations, and qa-1F mutants selectively deficient in the activation of these promoters have been identified. Therefore, the qa-1F regulatory gene appears to control two types of promoters that have different requirements for activation.