General activator of RNA polymerase III transcription. Factor exclusively required for RNA polymerase III transcription of genes with promoter elements upstream of the initiation sites. Contributes to the regulation of gene expression; functions as activator in the absence of oxidative stress. Down-regulates expression of target genes in response to oxidative stress. Overexpression protects cells against apoptosis in response to oxidative stress. Component of TFIIIB complexes. The TFIIIB complex has two activities, alpha and beta. The TFIIIB-alpha activity complex is composed of TBP, BDP1, and a complex containing both BRF2 and at least four stably associated proteins; this complex inhibits the transcription by pol III via its phosphorylation by CK2; YY1 facilitates the TFIIIB-alpha complex formation. Interacts with TBP; this interaction promotes recruitment of BRF2 to TATA box-containing promoters. Interacts with TBP and the BURE sequence (GC-rich sequence downstream from the TATA box) to form a strong ternary complex which is joined by BDP1; this ternary complex stimulates pol III transcription. Forms a trimeric complex composed of TBP, BRF2 and mini-SNAPc complex (SNAP43, SNAP50, and the N-terminal third of SNAP190) on the promoter. Assembly of the TBP-BRF2 complex is stimulated by SNAP190. Interacts with MAF1 and SNAPC4. In response to oxidative stress, Cys-363 is reversibly oxidized to cysteine sulfenic acid. Oxidation of Cys-363 impairs formation of a ternary complex with TBP and DNA and down-regulates expression of target genes in response to oxidative stress. Belongs to the TFIIB family.