POLR2I (RPB9) is a core component of RNA polymerase II, positioning itself in the upper jaw structure surrounding the central cleft to facilitate DNA template engagement. As part of the basal transcription machinery, it functions in transcription initiation, elongation, and fidelity maintenance, as well as transcription-coupled nucleotide-excision repair. Based on limited published evidence, POLR2I has been identified as a key regulatory node in coronary artery disease networks 1 and emerges as a novel gene associated with particulate matter-induced cardiac disease through altered methylation and transcriptional patterns 2.