Transcription factor IIIB 90 kDa subunit (BRF1)

General activator of RNA polymerase which uses different TFIIIB complexes at distinct promoters. The isoform 1 is involved in the transcription of tRNA, adenovirus VA1, 7SL and 5S RNA.

Isoform 2 is necessary for transcription of the U6 promoter. .