Structural studies of eukaryotic RNA polymerase II (Pol II) transcription often rely on in vitro assembly, which may not fully represent native conditions. To investigate Pol II transcription in metazoan cells, we developed a method to isolate native transcription complexes from Drosophila melanogaster embryos using FLAG-tag affinity purification and Micrococcal Nuclease treatment. Cryo-EM and proteomics studies revealed diverse transcription complexes and nucleosomes, including a metazoan Rpb4/Rpb7 stalk-less Pol II elongation complex and a hexameric nucleosome lacking an H2A/H2B dimer. Notably, nucleosome is found only downstream of the nucleosome elongation complex, underscoring it as a major energy barrier and a time-consuming step during Pol II progression through chromatin. Proteomics identified co-purified factors involved in transcription initiation, elongation, and RNA modification. This study provides a framework for investigations of transcription in cells, paving the way for future studies of transient and minor complexes. Here the authors show that native Pol II transcription complexes are isolated directly from D. melanogaster embryos by using a robust one-step affinity purification and by using cryo-EM resolve multiple functional states of the Pol II transcription complex and nucleosome.
Natalie L. Venette-Smith, R. Vishwakarma, Varun Venkatakrishnan et al.· Nature Communications· 0 citations
All cellular RNA polymerases (RNAPs) across Bacteria, Archaea, and Eukarya share a conserved catalytic core, yet bacterial and archaeal-eukaryotic RNAPs diverged after separation from the last universal common ancestor. This evolutionary split produced distinct subunit compositions and fundamentally different requirements for external factors during transcription initiation. Bacterial RNAP relies on a σ factor, whereas archaeal-eukaryotic RNAPs require a more extensive set of general transcription factors (GTFs) to bind promoter DNA, unwind the duplex, and position the template strand within the active site cleft. Notably, despite the close structural similarity between archaeal and eukaryotic RNAPs, the requirement for GTFs became further specialized after the emergence of Eukarya. This divergence raises the question of whether differences in intrinsic conformational flexibility and dynamics of these RNAPs contribute to distinct promoter-loading pathways. In this study, we addressed this question using cryo-electron microscopy (cryo-EM) to examine archaeal RNAPs from Euryarchaeota and Crenarchaeota alongside yeast RNAP II. Archaeal RNAP displays a highly dynamic DNA binding clamp domain that samples a broad spectrum of open and closed states, whereas RNAP II predominantly adopts a closed clamp state. Both archaeal and eukaryotic RNAPs can be found in stalk-bound and stalk-less forms. Comparative structural analyses further reveal a unique conformational transition in crenarchaeal RNAP associated with clamp opening. Together, these findings define the intrinsic clamp-conformational landscapes across the archaeal-eukaryotic lineage and suggest that evolutionary tuning of clamp flexibility and dynamics contributes to distinct GTF-dependent promoter-loading mechanisms.
George Nkansah Rost Fordjour, L. Palao, Kenji Murakami et al.· Journal of Biological Chemis...· 0 citations
We use cookies to run the site and, with your consent, for analytics and to show ads.
See our Cookie Policy.
