Region-specific transcriptional activity in the genome of Streptomyces coelicolor A3(2)

Transcriptional analysis of microbial genomes is an important component of functional genomics. Strategies such as hybridization of labeled total RNA against ordered clone libraries or differential- display approaches have al ready been carried out to identify expressed genes. We describe here an add itional method which applies subtractive hybridization between genome-speci fic DNA and total RNA followed by a PCR approach to identify expressed micr obial genes. With the new strategy, the expression of genes in the terminal regions of the linear Streptomyces coelicolor A3(2) chromosome and the acc essory linear plasmid SCP1 was analyzed. The results indicate that the meth od is useful for the identification of expressed genes in actinomycetes and other microbial systems. We demonstrate for the first time that at least 2 4 genes in the chromosome end regions (silent regions) of S. coelicolor are actively expressed. In addition, several expressed SCP1 genes were identif ied, including a gene which shows high similarity to microbial dnaN genes a nd which seems to play a role in SCP1 maintenance.