RNA polymerase (pol) III synthesizes tRNA, 5s rRNA, 7SL RNA and U6 snRNA and is overexpressed in many transformed cell lines and tumors in vivo, since cells must duplicate its protein components before division. Therefore, in order to maintain rapid growth, cells must produce a high level of Pol III transcribed RNA, which requires the presence of the TFIIIB and TFIIIC2 transcription factor complexes. The TFIIIC2 complex is composed of five subunits, TFIIIC220, TFIIIC110, TFIIIC102, TFIIIC90 and TFIIIC63, that are overexpressed in adenovirus transformed cells as well as in malignant cells in vivo, such as ovarian carcinomas. TFIIIC2 recruits RNA pol III and TFIIIB to promoter elements and may be a key component in the deregulation of malignant cells. The TFIIIB complex includes the TATA-binding protein (TBP), TFIIB-related factor 1 (TFIIIB90, BRF1) and TFIIIB, the expression of which are also upregulated in transformed cells. In many carcinomas, the tumor suppressors retinoblastoma (RB) and p53 are inactivated, which affects their ability to bind and inactivate the function of TFIIIB.
B - related factor 1; B-related factor 1; BRF-1; BRF1 homolog, subunit of RNA polymerase III transcription initiation factor IIIB; epididymis secretory sperm binding protein Li 76p; general transcription factor IIIB, 90kD subunit; hTFIIIB90; TAF3B2; TATA box binding protein (TBP)-associated factor 3C; TATA box binding protein (TBP)-associated factor, RNA polymerase III, GTF3B subunit 2; TATA box-binding protein-associated factor, RNA polymerase III, subunit 2; TBP - associated factor, RNA polymerase III, 90kD; TFIIIB90; Transcription factor IIIB 90 kDa subunit