CELL-CYCLE REGULATION OF RNA-POLYMERASE-III TRANSCRIPTION

Inactivation of the TATA-binding protein-containing complex TFIIIB con tributes to the mitotic repression of RNA polymerase III transcription , both in frogs and in humans (J, M, Gottesfeld, V, J, Wolf, T. Dang, D. J. Forbes, and P, Hartl, Science 263:81-84, 1994; R. J, White, T. M . Gottlieb, C. S, Downes, and S, P, Jackson, Mel. Cell, Biol, 15:1983- 1992, 1995). Using extracts of synchronized proliferating HeLa cells, we show that TFIIIB activity remains low during the early part of G(1) phase and increases only gradually as cells approach S phase, As a re sult, the transcription of all class III genes tested is significantly less active in early G(1) than it is in S or G(2) phase, both in vitr o and in vivo, The increased activity of TFIIIB as cells progress thro ugh interphase appears to be due to changes in the TATA-binding protei n-associated components of this complex, The data suggest that TFIIIB is an important target for the cell cycle regulation of RNA polymerase III transcription during both mitosis and interphase of actively prol iferating HeLa cells.