Genome organization in Mycoplasma hyopneumoniae: identification of promoter-like sequences.

Information related to open reading frame (ORF) organization, transcription regulation and promoter sequence has been available for the Mycoplasma hyopneumoniae 7448 genome, demonstrating that the ORFs are continuously transcribed (cotranscription) in large clusters. A species-specific position-specific scoring matrix was applied to scan for putative promoters upstream of all coding sequences on a genome scale in M. hyopneumoniae. This study consisted of a detailed in silico promoter localization analysis by scanning the position-specific promoters upstream of predicted ORF clusters (OCs) and mCs (monocistronic genes) in the M. hyopneumoniae whole genome; this was combined with experimental data for the promoterless ORFs. Promoter-like sequences were found in 86% of the OCs (from the OC first gene) and in 85% of the mCs. A transcription analysis of the promoterless ORF was performed by RT-PCR. This strategy allowed the definition of a specific promoter sequence for all OCs and mCs indicating that all the transcriptional units are preceded by putative promoter sequences (matrix and manually located) and providing evidence for functional gene organization in the M. hyopneumoniae genome. These results shown that the species-specific, position-specific scoring matrix for promoter prediction is effective, further increasing the knowledge of gene organization and transcription initiation in mycoplasmas.