Transcriptional coactivator that stimulates transcriptional activity by bridging regulatory proteins and TBP, thereby recruiting TBP to promoters occupied by DNA-binding regulators. Expressed in leaves, roots, stems, flowers, siliques and shoots. Detected only in anthers and some seeds in siliques. Detected in some seeds from 3 days after pollination (dap) to 11 dap. Not induced by heat or cold treatments, H(2)O(2), dehydration, abscisic acid, 2,4-D, ACC, methyl jasmonate or salicylic acid. Weak induction by salt stress and pathogen induction. The C-terminal domain (75-142) is essential for nucleolar localization. Belongs to the MBF1 family.