Book of Abstracts: Albany 2011
June 14-18 2011
©Adenine Press (2010)
DNA Recognition in RNA Polymerase III Transcription
Eukaryotic transcription requires the coordinated activities of enhancers that recognize specific DNA target sites, co-activators and general transcription factors to recruit RNA polymerases to their transcription start sites (1). Among the three eukaryotic RNA polymerases, recruitment of RNA polymerase II is by far the most complex process requiring a large number of different factors. In comparison, recruitment of RNA polymerase I and III is simpler and therefore more amenable for detailed structure-function analyses. RNA polymerase I and III are responsible for producing non-coding RNAs such as pre-RNA and tRNA. Together, they contribute up to 80% to the total transcriptional activity in growing cells and need to be tightly regulated. In the last years there has been increasing awareness that mis-regulation of RNA polymerase I and III is associated with different types of cancer (2).
Recruitment of RNA polymerase III to the transcription start site requires binding of the general transcription factors TFIIIB and TFIIIC. TFIIIC is a large DNA-binding complex with a total molecular weight of 0.6 MDa composed of six polypeptides. TFIIIC can be subdivided into two subcomplexes, that initiate RNA polymerase III transcription by binding to two internal promoter sites in tRNA genes named A¬¬¬- and B-box. We are using a combination of X-ray crystallography, electron microscopy and biochemistry to gain insights into the structural organization of the RNA polymerase III enzyme and its general transcription factors (3-5). During the last years our group has determined crystal structures corresponding to ~2/3 of the entire TFIIIC complex and obtained a low-resolution EM reconstruction of TFIIIC that serves as a starting point to assemble the entire complex. We will present insights into DNA recognition by the RNA polymerase III-specific general transcription factor complex TFIIIC resulting from this studies.
Structural and Computational Biology Unit