Promoters of the CATG-Specific Methyltransferase Gene hpyIM Differ between iceA1 and iceA2 Helicobacter pylori Strains

Abstract

Helicobacter pylori strains can be divided into two groups, based on the presence of two unrelated genes, iceA1 and iceA2, that occupy the same genomic locus. hpyIM , located immediately downstream of either gene, encodes a functional CATG-specific methyltransferase. Despite the strong conservation of the hpyIM open reading frame (ORF) among all H. pylori strains, the sequences upstream of the ORF in iceA1 and iceA2 strains are substantially different. To explore the roles of these upstream sequences in hpyIM regulation, promoter analysis of hpyIM was performed. Both deletion mutation and primer extension analyses demonstrate that the hpyIM promoters differ between H. pylori strains 60190 ( iceA1 ) and J188 ( iceA2 ). In strain 60190, hpyIM has two promoters, P _a or P _I , which may function independently, whereas only one hpyIM promoter, P _c , was found in strain J188. The XylE assay showed that the hpyIM transcription level was much higher in strain 60190 than in strain J188, indicating that regulation of hpyIM transcription differs between the H. pylori iceA1 strain (60190) and iceA2 strains (J188). Since the iceA1 and iceA2 sequences are highly conserved within iceA1 or iceA2 strains, we conclude that promoters of the CATG-specific methylase gene hpyIM differ between iceA1 and iceA2 strains, which leads to differences in regulation of hpyIM transcription.