DNA methyltransferases and DNA methylation in helicobacter pylori
Student name: Ms Deepika Jaiman
Guide: Dr Ramakrishnan Sitaraman
Year of completion: 2013
Host Organisation: TERI University
Abstract: Helicobacter pylori is known to be the causative agent of gastric carcinomas and is present in half of
the world population. Its niche is human gastric mucosa, which was earlier thought to be devoid of
any living organisms. Genomic analysis of H. pylori 26695 and J99 strain showed presence of 25 and
29 putative MTases respectively, in them. Several of them lack cognate restriction endonuclease
which point towards their role in biological functions other than defence against invading genomes.
One of them is shown to be a phasevarion controlling expression of genes encoding proteins for
adherence and persistence. Presence of more than 20 dozen R-M systems provides formidable
barrier against transformation and strain-specific variation in MTases provides differential donor
DNA susceptibilities to restriction endonuclease digestion during inter-strain transfer. These, factors
render transformation refractory which is the prerequisite to do genetic manipulation in an organism
to study its genetic traits. So, in order to study role of MTases regulating important biological
functions like virulence or to avoid restriction barrier through methylation of vectors, functional
characterisation of putative MTases for their sequence specificities, positions and base specificities
need to be elucidated. Present work aims towards developing an expression vector system to screen
for putative adenine and cytosine MTases from H.pylori.
Key words – Epigenetics, DNA Methylation, Methyltransferases, orphan MTases and Methylation
patterns.
