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Open Access Research article

Rrd1 isomerizes RNA polymerase II in response to rapamycin

Nathalie Jouvet1, Jeremie Poschmann2, Julie Douville1, Lisa Bulet1 and Dindial Ramotar1*

Author Affiliations

1 Maisonneuve-Rosemont Hospital, Research Center, Department of Immunology and Oncology, University of Montreal, 5415 de l'Assomption, Montreal, Quebec, Canada, H1T 2M4

2 Genome Institute Singapore, 60 Biopolis Street, #02-01, Genome, Singapore 138672

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BMC Molecular Biology 2010, 11:92  doi:10.1186/1471-2199-11-92

Published: 3 December 2010

Abstract

Background

In Saccharomyces cerevisiae, the immunosuppressant rapamycin engenders a profound modification in the transcriptional profile leading to growth arrest. Mutants devoid of Rrd1, a protein possessing in vitro peptidyl prolyl cis/trans isomerase activity, display striking resistance to the drug, although how Rrd1 activity is linked to the biological responses has not been elucidated.

Results

We now provide evidence that Rrd1 is associated with the chromatin and it interacts with RNA polymerase II. Circular dichroism revealed that Rrd1 mediates structural changes onto the C-terminal domain (CTD) of the large subunit of RNA polymerase II (Rpb1) in response to rapamycin, although this appears to be independent of the overall phosphorylation status of the CTD. In vitro experiments, showed that recombinant Rrd1 directly isomerizes purified GST-CTD and that it releases RNA polymerase II from the chromatin. Consistent with this, we demonstrated that Rrd1 is required to alter RNA polymerase II occupancy on rapamycin responsive genes.

Conclusion

We propose as a mechanism, that upon rapamycin exposure Rrd1 isomerizes Rpb1 to promote its dissociation from the chromatin in order to modulate transcription.