Appears to be stable component of the Pol II(G) complex form of RNA polymerase II. Pol II synthesizes mRNA precursors and many functional non-coding RNAs and is the central component of the basal RNA polymerase II transcription machinery. May play a role in Mediator-dependent regulation of transcription activation. In vitro, acts as negative regulator of transcriptional activation; this repression is relieved by the Mediator complex, which restores Pol II(G) activator-dependent transcription to a level equivalent to that of Pol II (By similarity). Component of the Pol II(G) complex, which contains the RNA polymerase II (Pol II) core complex subunits and POLR2M and appears to be an abundant form of Pol II. Belongs to the GRINL1 family.