The function of POLR2I (RNA polymerase II subunit I, Ensembl gene identifier ENSG00000105258) is as follows. Core component of RNA polymerase II (Pol II), a DNA-dependent RNA polymerase which synthesizes mRNA precursors and many functional non-coding RNAs using the four ribonucleoside triphosphates as substrates. Pol II is the central component of the basal RNA polymerase II transcription machinery. It is composed of mobile elements that move relative to each other. POLR2I/RPB9 is part of the upper jaw surrounding the central large cleft and thought to grab the incoming DNA template. {ECO:0000250|UniProtKB:P27999, ECO:0000269|PubMed:27193682, ECO:0000269|PubMed:30190596, ECO:0000269|PubMed:9852112}.