Details

Autor(en) / Beteiligte

• HUIET, RUTH LAYNE

Titel

GENETIC ORGANIZATION AND NUCLEOTIDE SEQUENCE OF THE QA-1S AND QA-1F REGULATORY GENES OF NEUROSPORA CRASSA

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

1983

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• The lower eukaryote Neurospora crassa can utilize quinic acid as a sole carbon source. Initial genetic biochemical studies indicated that four genes (qa genes) were required for the first three steps in quinic acid degradation and that these four genes were tightly clustered on chromosome VII. Three of these are structural genes which are coordinately induced by quinic acid and the regulation of enzyme synthesis is at the transcriptional level. The fourth gene, qa-1, controls the transcription of the qa structural genes. Previous genetic analysis identified two types of mutants which mapped to non-overlapping regions and which were interpreted to define separate domains of a single regulatory protein. A DNA fragment comprising the entire qa gene cluster has previously been cloned in E. coli and the qa-1 gene localized by transformation of Neurospora. This dissertation describes the detailed physical characterization of the qa-1 region. Using both Neurospora transformation and DNA-RNA hybridization it has been demonstrated that the qa-1 region consists of two distinct genes corresponding to the two original mutational types qa-1('S) and qa-1('F), now designated qa-1S and qa-1F respectively. Based upon these and earlier genetic data, it is proposed that the qa-1F genes encodes a positive regulatory protein which controls transcription of the structural genes as well as itself. The qa-1S gene, on the other hand, is believed to encode a repressor which interacts with the inducer quinic acid and which controls the expression of qa-1F and possibly also the structural genes. The complete sequence of the region containing both of these genes has been determined. Potential coding regions have been identified and correspond to protein of 100,000 M(,r) for qa-1S and 88,000 M(,r) for qa-1F. Using mRNA mapping procedures the 5' ends of the transcripts have been localized and a small (45 bp) intervening sequence identified in qa-1S. The two genes are separated by only 380 bp and are transcribed in divergent directions, raising the possibility that the genes may share a common regulatory region.