Transcriptional analysis and regulatory signals of the hom-thrB cluster of XXXX .

@entity9150 @entity21812 @entity1889 @entity526
Two genes, hom (encoding @entity21812 dehydrogenase) and thrB (encoding @entity21812 kinase), of the @entity1889 biosynthetic pathway are clustered in the chromosome of @entity9150 in the order 5' hom-thrB 3', separated by only 10 bp. The Brevibacterium thrB gene is expressed in @entity526 , in @entity9150 , and in @entity9150 and complements auxotrophs of all three organisms deficient in @entity21812 kinase, whereas the Brevibacterium hom gene did not complement two different @entity526 auxotrophs lacking @entity21812 dehydrogenase. However, complementation was obtained when the @entity21812 dehydrogenase was expressed as a fusion protein in @entity526 . Northern (RNA) analysis showed that the hom-thrB cluster is transcribed, giving two different transcripts of 2.5 and 1.1 kb. The 2.5-kb transcript corresponds to the entire cluster hom-thrB (i.e., they form a bicistronic operon), and the short transcript (1.1 kb) originates from the thrB gene. The promoter in front of hom and the hom-internal promoter in front of thrB were subcloned in promoter-probe vectors of @entity526 and corynebacteria. The thrB promoter is efficiently recognized both in @entity526 and corynebacteria, whereas the hom promoter is functional in corynebacteria but not in @entity526 . The transcription start points of both promoters have been identified by primer extension and S1 mapping analysis. The thrB promoter was located in an 87-bp fragment that overlaps with the end of the hom gene. A functional transcriptional terminator located downstream from the cluster was subcloned in terminator-probe vectors.
