Comparative Analysis of Mycoplasma gallisepticum vlhA Promoters

Abstract

Mycoplasma gallisepticum is an intracellular parasite affecting respiratory tract of poultry that belongs to class Mollicutes. M. gallisepticum features numerous variable lipoprotein hemagglutinin genes (vlhA) that play a role in immune escape. The vlhA promoters have a set of distinct properties in comparison to promoters of the other genes. The vlhA promoters carry a variable GAA repeats region at approximately 40 nts upstream of transcription start site. The promoters have been considered active only in the presence of exactly 12 GAA repeats. The mechanisms of vlhA expression regulation and GAA number variation are not described. Here we tried to understand these mechanisms using different computational methods. We conducted a comparative analysis among several M. gallisepticum strains. Nucleotide sequences analysis showed the presence of highly conserved regions flanking repeated trinucleotides that are not linked to GAA number variation. VlhA genes with 12 GAA repeats and their orthologs in 12 M. gallisepticum strains are more conserved than other vlhA genes and have narrower GAA number distribution. We conducted comparative analysis of physicochemical profiles of M. gallisepticum vlhA and sigma-70 promoters. Stress-induced duplex destabilization (SIDD) profiles showed that sigma-70 group is characterized by the common to prokaryotic promoters sharp maxima while vlhA promoters are hardly destabilized with the region between GAA repeats and transcription start site having zero opening probability. Electrostatic potential profiles of vlhA promoters indicate the presence of the distinct patterns that appear to govern initial stages of specific DNA-protein recognition. Open state dynamics profiles of vlhA demonstrate the pattern that might facilitate transcription bubble formation. Obtained data could be the basis for experimental identification of mechanisms of phase variation in M. gallisepticum.

Systematic Analysis of REBASE Identifies Numerous Type I Restriction-Modification Systems with Duplicated, Distinct hsdS Specificity Genes That Can Switch System Specificity by Recombination

“…SSR tracts located in the open reading frame of a gene can result in the gene being in frame and expressed (ON) or, due to a frameshift downstream of the SSR tract, out of frame and not expressed (OFF). SSR tracts also occur in the promoter of a number of genes ( 9 – 11 ), and variation in length of these SSRs can lead to ON-OFF switching of gene expression or result in a gradient of high- to low-level expression dependent on the length of the SSR tract ( 12 ). Several bacterial pathogens also contain well-characterized cytoplasmic N 6 -adenine DNA methyltransferases, which are part of restriction-modification (R-M) systems, that exhibit phase-variable expression.…”

Seroprevalence of Mycoplasma gallisepticum in Commercial Broiler Chickens in Duhok Governorate

“…The pathogens of mycoplasma are gram negative and they belong to class Mollicutes, order-I Mycoplasmatales, family-I Mycoplasmataceae and genus Mycoplasma. Mycoplasma gallisepticum (MG) are small size bacteria, without having cell wall and having a triple layers of plasma membrane [2,3]. (MG) is the most common pathogenic mycoplasmas in broiler and layer production.…”