AUTHOR=Ta Linda H., Hansen Lori M., Sause William E., Shiva Olga , Millstein Aram , Ottemann Karen M., Castillo Andrea R., Solnick Jay V.

TITLE=Conserved Transcriptional Unit Organization of the Cag Pathogenicity Island among Helicobacter pylori Strains

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=2

YEAR=2012

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2012.00046

DOI=10.3389/fcimb.2012.00046

ISSN=2235-2988

ABSTRACT=<p>The <italic>Helicobacter pylori</italic><italic>cag</italic> pathogenicity island (<italic>cag</italic> PAI) encodes a type IV secretion system that is more commonly found in strains isolated from patients with gastroduodenal disease than from those with asymptomatic gastritis. Genome-wide organization of the transcriptional units in <italic>H. pylori</italic> strain 26695 was recently established using RNA sequence analysis (Sharma et al., <xref ref-type="bibr" rid="B26">2010</xref>). Here we used quantitative reverse-transcription polymerase chain reaction of open reading frames and intergenic regions to identify putative <italic>cag</italic> PAI operons in <italic>H. pylori</italic>; these operons were analyzed further by transcript profiling after deletion of selected promoter regions. Additionally, we used a promoter-trap system to identify functional <italic>cag</italic> PAI promoters. The results demonstrated that expression of genes on the <italic>H. pylori</italic><italic>cag</italic> PAI varies by nearly five orders of magnitude and that the organization of <italic>cag</italic> PAI genes into transcriptional units is conserved among several <italic>H. pylori</italic> strains, including, 26695, J99, G27, and J166. We found evidence for 20 transcripts within the <italic>cag</italic> PAI, many of which likely overlap. Our data suggests that there are at least 11 operons: <italic>cag1-4</italic>, <italic>cag3-4</italic>, <italic>cag10-9</italic>, <italic>cag8-7</italic>, <italic>cag6-5</italic>, <italic>cag11-12</italic>, <italic>cag16-17</italic>, <italic>cag19-18</italic>, <italic>cag21-20</italic>, <italic>cag23-22</italic>, and <italic>cag25-24</italic>, as well as five monocistronic genes (<italic>cag4</italic>, <italic>cag13</italic>, <italic>cag14</italic>, <italic>cag15</italic>, and <italic>cag26</italic>). Additionally, the location of four of our functionally identified promoters suggests they are directing expression of, in one case, a truncated version of <italic>cag26</italic> and in the other three, transcripts that are antisense to <italic>cag7</italic>, <italic>cag17</italic>, and <italic>cag23</italic>. We verified expression of two of these antisense transcripts, those antisense to <italic>cag17</italic> and <italic>cag23</italic>, by reverse-transcription polymerase chain reaction. Taken together, our results suggest that the <italic>cag</italic> PAI transcriptional profile is generally conserved among <italic>H. pylori</italic> strains, 26695, J99, G27, and J166, and is likely complex.</p>