Eichhorn K and Jackson SP. (2001) A role for TAF3B2 in the repression of human RNA polymerase III transcription in non-proliferating cells. J. Biol. Chem. 276:21158-21165.

RNA polymerase III (Pol III) synthesizes various small RNA species, including the transfer RNAs (tRNAs) and the 5S ribosomal RNA, which are involved in protein synthesis. Here, we describe the regulation of human Pol III transcription in response to sustained cell cycle arrest. The experimental system used is a cell line in which cell cycle arrest is induced by the regulated expression of the tumour suppressor protein p53. We show that the capacity of cells to carry out Pol III transcription from various promoter types, when tested in vitro, is severely reduced in response to sustained p53-mediated cell cycle arrest. Furthermore, this effect does not appear to be due to direct inhibition by p53. By using complementation assays, we demonstrate that a sub-component of the Pol III transcription factor IIIB (TFIIIB), which contains the proteins TBP and TAF3B2, is the target of repression. Moreover, we reveal that TAF3B2 levels are markedly reduced in extracts from cell cycle arrested cells due to a decrease in TAF3B2 protein stability. These findings provide a novel mechanism of Pol III regulation and yield insights into how cellular biosynthetic capacity and growth status can be co-ordinated.