Identificação de regiões promotoras de Mycoplasma hyopneumoniae

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

2012

RESUMO

Mycoplasma hyopneumoniae is one of the smallest bacteria found in nature, presenting a small genome and absence of cell wall. It is present in the majority of swine herds throughout the world, and is considered an important pathogen in the swine industry. In the last decade, many species of this genus had their genome completely sequenced, including four strains of M. hyopneumoniae. Nevertheless, very little is understood of the nucleotide sequences that control transcription initiation in these microorganisms. Like its relatives, M. hyopneumoniae lacks several major regulators of gene expression, including two component regulatory systems and multiple ¿ factors, thus it appears that the signals for promotion and regulation of transcription may differ significantly from other bacteria. In addition, the low GC content and the dearth of experimentally characterized promoters in this genus severely limit the recognition of the controlling sequences. Therefore, this study aims to identify nucleotide sequences involved in transcription initiation in M. hyopneumoniae, and thus generate data to enable the construction of a matrix capable of predicting promoters in this species. Initially, the transcription start sites (TSSs) of 23 genes of M. hyopneumoniae were experimentally defined. The results showed that the identified TSSs were located between 2 and 144 bp away from the gene starts, being composed mostly of an adenosine residue. A pattern that resembles the ¿70 promoter ¿10 element was found upstream of the TSSs. However, no ¿35 element was distinguished. Instead, an AT-rich periodic signal was identified. About half of the experimentally defined promoters contained the motif 5 -TRTG-3 , which was identical to the ¿16 element usually found in gram-positive bacteria. The defined promoters were utilized to build position-specific scoring matrices in order to scan putative promoters upstream of all coding sequences (CDSs) in the M. hyopneumoniae genome. Two hundred and one signals were found associated with 169 CDSs. Most of these sequences were located within 100 nucleotides of the start codons. This study has shown that the number of promoter-like sequences in the M. hyopneumoniae genome is more frequent than expected by chance, indicating that most of the sequences detected are probably biologically functional.

ASSUNTO(S)

mycoplasma hyopneumoniae

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