In a variety of tumours, CDK9-mediated phosphorylation of RNA Pol II Ser2 and MLL1-mediated regulation of H3K4me3 allow for hypermethylation of CGIs in exons of the HOTAIR gene, facilitating the transcriptional elongation process and promoting HOTAIR overexpression, which in turn mediates tumour development [113]. The gene discussed is HOTAIR; the disease is neoplasm.