We have investigated in the yeast Saccharomyces cerevisiae the mechanisms by which the Mediator, a 25 subunits complex, stimulates the transcription by RNA polymerase (Pol) II of activated genes. We identified a contact between Pol II and the Mediator in vivo and demonstrated that this contact is essential for the transcription of essentially all genes in vivo.In a second study, Pol III is known to transcribe the tRNAs, the 5S ribosomal RNA and some small stable RNAs. Two transcription factors, TFIIIB and TFIIIC, assist the enzyme in the recognition of the class III genes. We have investigated the Pol III transcriptome in mouse ES cells using a tandem ChIP-Seq method, looking at the genomic distribution of Pol III and its factors.

We found that only a subset of the annotated tRNAs are transcribed in mouse ES cells. Moreover, we found that a small subset of the SINEs are transcribed. We also demonstrated that the TFIIS Pol II elongation factor is also present on actively transcribed genes indicating that it is probably also a Pol III transcription factor.

Selected references:

Esnault, C., Ghavi-Helm, Y., Brun, S., Soutourina, J., van Berkum, N., Boschiero, C, Holstege, F. and Werner, M. (2008) Mediator-dependent recruitment of TFIIH modules in preinitiation complex. Mol. Cell. 31, 337-346.

Ghavi-Helm, Y., Michaut, M., Acker, J., Aude, J.-C., Thuriaux, P., Werner, M.* and Soutourina, J.* (2008) Genome-wide location analysis of TFIIS in RNA polymerase III transcription. Genes Dev. 22, 1934-1947. IF=14.20

Soutourina, J.*, Wydau, S., Ambroise, Y., Boschiero, C. and Werner, M.* (2011) Direct RNA polymérase II – Mediator interaction required for transcription in vivo. Science, 331, 1451-1454.