Hydroxymethylation and its potential implication in DNA repair system: A review and future perspectives

The 5-hydroxymethylcytosine (5-hmC) is known to exist as a predictive indicator for a variety of cancers, neurological abnormalities and other perilous diseases. The precursor of 5-hmC i.e. 5-methylcytosine (5mC) has already gained attention as an important epigenetic regulator whereas 5-hmC remains less explored. The two modified DNA bases (5mC and 5-hmC) have absolute diverse distribution, i.e. 5-hmC is mostly restrained to the 5' end of DNA with levels directing the gene transcription whereas 5mC is mainly located at the intra- or intergenic regions of DNA repeats and within certain gene bodies. It has been reported that levels of 5-hmC in different tissues provide a useful tool for detecting numerous associated diseases and their progression. Therefore, to unravel the role of hydroxymethylation in various resulting diseases in humans, comprehensive information on this crucial process has been explored and compiled for its implication in DNA repair system. The role of miRNAs in cancer through hypo- and hypermethylation has also been explored and discussed. In this review, a broad and exclusive insight into hydroxymethylation and its association with repair mechanisms is extensively presented and it is estimated that the accessible information will be of utmost use to the biological community working in the relevant research area.