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 (PubMed:11040218, PubMed:11121026, PubMed:11564744, PubMed:26638071). Contributes to the regulation of gene expression; functions as activator in the absence of oxidative stress (PubMed:26638071). Down-regulates expression of target genes in response to oxidative stress (PubMed:26638071). Overexpression protects cells against apoptosis in response to oxidative stress (PubMed:26638071). {ECO:0000269|PubMed:11040218, ECO:0000269|PubMed:11121026, ECO:0000269|PubMed:11564744, ECO:0000269|PubMed:26638071}. This is the function of ENSG00000104221 (BRF2, BRF2 general transcription factor IIIB subunit).