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Host genomic regions susceptible to damage during H. pylori infection

ABSTRACT: We identify here host genomic regions that are more likely to be damaged during an infection with the human gastirc pathogen Helicobacter pylori and characterize underlying features of them. By ChIP-seq we obtained global information about the localization of the DNA-damage marker H2AXpS139. We used 20 ng of immunoprecipitated DNA of the human gastric cell line AGS to produce 240 mio sequence reads in total and compared the damage-pattern of 6 h and 19 h infected cells with that of 10 Gy irradiated ones. While the overall levesl of DNA damage wetre similar in terms of broken DNA and accumulation of H2AXpS139, infection-induced damage clearly accumulates towards the ends of chromosomal arms, namely telomere-proximal and close to centromeres, it also enriches mainly in genic and especially in transcribed regions. We show, taht this damage pattern is unique to the infection, occurs also in human non-transformed gastric epithelial cells and shows some correlation with previously identified cancer-related genes.

ORGANISM(S): Homo sapiens

PROVIDER: GSE55699 | GEO | 2015/05/18

SECONDARY ACCESSION(S): PRJNA240573

REPOSITORIES: GEO

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Project description:Helicobacter pylori infection promotes chronic inflammation and plethora of DNA damages including strand breaks, base alterations, point mutations, microsatellite instability and epigenetic alterations. The gastric epitheliaI cells, in order to prevent genomic instability, require an integrous DNA damage repair (DDR) machinery which, however, has been reported to be modulated by the infection. CagA is a major Hp virulence factor that deregulates host cell functions such as proliferation, apoptosis and chromosomal integrity. Its pathogenic activity is partly regulated by tyrosine phosphorylation on repeated EPIYA-motifs. Our aim was to identify putative effects of H. pylori infection and CagA protein on DDR machinery, investigating the transcriptome of AGS cells, infected with P12 H. pylori wild-type strain, as well as, its corresponding CagA knock-out and the CagA phosphorylation-defective mutant following tyrosine (EPIYA) substitution by phenylalanine (EPIFA) in the EPIYA-C motifs. Upon RNA-Sequencing on polyA-selected transcripts we performed Differential Expression Analysis, Pathway Enrichment Analysis and visualization on KEGG Pathway Maps per DDR mechanism. Key DDR components that were observed to be downregulated in a CagA-related manner were validated via Western Blot utilizing AGS and the non-cancerous GES1 cell lines. Transcriptome analysis revealed that a notable number of DDR genes were downregulated during H. pylori infection resulting to potential modulation of Base Excision Repair, Mismatch Repair and a more intricate deregulation of Nucleotide Excision Repair, Homologous Recombination and Non-Homologous End-Joining. CagA contributes to MUTYH, FEN1, APE1, POLD1 and LIG1 downregulation and those observations were verified on the protein expression level, with the exception of APE1 that was on contrary observed to be upregulated. Our study accentuates the role of CagA, as a significant contributor of the H. pylori infection-mediated DDR modulation, disrupting the balance between DNA damage introduction and repair thus favoring genomic instability and potentially contributing to gastric carcinogenesis.

Project description:Background: Helicobacter pylori is an important human pathogen that infects the human gastric mucosa leading to chronic inflammation which is responsible for severe gastroduodenal diseases. The Outer Inflammatory Protein A (OipA) of H. pylori is an important virulence factor. However, the role of OipA in gastric cancer and ulcer development is still not well-established. Phase variation within a CT dinucleotide repeat motif of oipA switches its expression “on” and “off”. This study aims to elucidate the role of OipA in H. pylori infection using oipA “on” and “off” clinical strains and oipA deletion mutant. Methods: Proteomics analysis was performed on AGS human gastric epithelial cell line post-infection with oipA “on” and “off” H. pylori using liquid chromatography / mass spectrometry (LC/MS). In addition, AGS apoptosis and cell cycle assays were performed. To confirm the findings, oipA deletion mutant (ΔoipA) was generated and expression of VacA was detected using Western blotting. Result: Expression of AGS proteins involve in human disease was suppressed / down-regulated post-infection with oipA “off” strains, as well as oipA mutant, compared to oipA “on” strains. Furthermore, oipA “off” strains and oipA mutant resulted in a higher level of apoptosis and G0/G1 cell-cycle arrest in AGS cells than oipA “on” strains. Interestingly, deletion of oipA was found to increase VacA production by the bacterium. Discussion: The capability of oipA “off” strains to induce apoptosis and suppress proteins having roles in human disease may suggest that these H. pylori may be less virulent or may even be protective against carcinogenesis compared to its oipA “on” counterparts. This may potentially explain the higher incidence of gastric cancer among East Asian which oipA “on” strains predominates. Conclusions: Data from this study strengthened our understanding of the role of H. pylori OipA as a virulence factor in chronic inflammation, metastasis and carcinogenesis.

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Host genomic regions susceptible to damage during H. pylori infection

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