Epigenetic modifications contain three main processes: DNA methylation, histone modifications, and silencing by microRNAs.
Twenty-four-nucleotide heterochromatic siRNAs associated with the RITS complex facilitate chromatin modification and transcriptional silencing.
21-nt siRNAs are believed to guide mRNA cleavage, whereas 24-nt siRNAs are believed to exclusively mediate chromatin modification and transcriptional silencing by acting in a RISC-like complex (Brodersen and Voinnet 2006).
Deoxyribonucleic acid (DNA) methylation, histone modification, and gene silencing are involved in cancer pathogenesis.
Therefore, ncRNAs play direct roles in DNA methylation, heterochromatin formation, histone modification and gene silencing.
However, depending on the insertion site, higher copy number can also result in epigenetic modification and transgene silencing [ 8].
Such regulations are usually achieved by mediating endogenous mRNA cleavage and decay, DNA methylation of source and target loci, and chromatin modification and transcriptional silencing (Arikit et al., 2013).
Jones et al. demonstrated that trichostatin A (TSA), a HDAC inhibitor, relieves transcriptional repression at methylated CpG islands, and implicated that DNA methylation provided the nucleosomal infrastructure for HDAC-dependent chromatin modification and transcriptional silencing [ 34, 47].
For example, lmx1b showed a pattern of decreasing transcript abundance, as did several other genes that function in chromatin organization, modification, and gene silencing (e.g. dnmt1, baz1b, baz1a, smarca5, hist1h1b, hist1hbj, hist2h2ac).
In addition methylation is known to be involved in control of gene expression in many organisms and these enzymes may be involved in such a process during CPt10 infection, either through modification of its own DNA or by modification and possibly silencing of host gene expression.
