Length of thymidine homopolymeric repeats modulates promoter activity of sabA in Helicobacter pylori

Cheng Yen Kao, Shew Meei Sheu, Bor Shyang Sheu, Jiunn Jong Wu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Background: Helicobacter pylori uses SabA to interact with sialyl-Lewis x on the gastric mucosal surface to establish persistent colonization. The number of CT repeats in sabA is variable and thus influences SabA translation, but the expression of SabA determined by Western blotting does not fully match with a CT sequence-based prediction. Furthermore, a homopolymeric thymidine (polyT) tract located upstream of sabA has been observed, but its role in regulating sabA expression is still unknown. Methods: The transcriptional start site (TSS) of sabA in strains J99 and Hp258 was determined by 5' RACE. One hundred and fifteen clinical isolates were sequenced to analyze the distribution of the polyT tract length and promoter sequence. Finally, RT-PCR and an E. coli-lux reporter system were used to determine the sabA promoter activity with different lengths of the polyT tract. Results: The TSS of sabA was located at 66 or 64bp upstream of the translational start codon in J99 and Hp258, respectively. The polyT tract close to the -35 element varied from T 10 to T 28 in 115 clinical isolates, and 70% of the isolates contained a stretch of 14-19 Ts. The sabA gene displayed slipped strand mispairing (SSM) of the polyT tract, generating varying genotypes in J99 (16-18 Ts) and Hp258 (14-15 Ts). Furthermore, J99 with lengths of T 16 and T 30, had higher sabA promoter activity than the common length of T 18. Conclusion: Our findings indicate that the sabA promoter region modulates its transcriptional activity through a variable polyT tract, and SSM generates mixed genotypes in the population.

Original languageEnglish
Pages (from-to)203-209
Number of pages7
Issue number3
StatePublished - Jun 2012


  • Helicobacter pylori
  • SabA
  • Slipped strand mispairing


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