The transfer of genetic information encoded in DNA is the main determinant of gene expression. Alterations in this process have significant impact on cell homeostasis and are directly related to disease. RNA polymerases transcribe the genetic information from DNA to RNA, by catalyzing the addition of nucleotides that are complementary to the DNA template strand. Eukaryotes require three different RNA polymerases, each transcribing a specific set of genes and regulated by distinctive transcription factors. Our group has made relevant contributions in the structural and functional characterization of these essential enzymes and their regulatory factors.
RNA polymerase I (Pol I) is a cellular machine devoted to transcription of ribosomal RNA genes. Regulation defects in Pol I transcription associate with problems in cell proliferation and, hence, with tumor development. We pioneered the structural characterization of Pol I using X-ray crystallography, which unveiled fundamental properties of the enzyme [Nature, 2013]. We also used cryo-EM to obtain the structures of Pol I in the free monomeric state and in complex with the activating factor Rrn3 [eLife, 2017]. In vivo studies allowed us to propose a model for enzyme hibernation and reactivation, depending on external conditions [Transcription, 2018]. We also participated in the identification of a super-active Pol I mutant with biotechnological applications [PLoS Genet, 2019].
We also characterized transcription factors that regulate gene expression by RNA polymerase II (Pol II), which synthesizes messenger RNA in eukaryotic cells. We used biochemistry in combination with advanced NMR studies to unveil structural determinants in the disordered domain of CHOP, a transcription factor of the C/EBP family [PLoS One, 2017]. We further participated in the functional characterization of Sub1 in complex with Pol II [NAR, 2017] and in determining the X-ray structure of a transcription factor that regulates Pol III initiation [JBC, 2013]. We also collaborated in an X-ray structural study on bacterial RNA polymerase transcription initiation [JBC, 2014]. Additionally, we made methodological advances that can be applied in the X-ray analysis of large macromolecular assemblies [Acta Cryst D, 2014]. In the past, we have been interested in the cryo-EM characterization of RNA polymerase III (Pol III), which produces transfer RNAs and the 5S ribosomal RNA [RNA Biol, 2011; EMBO J, 2010].