Transcription in the cell is performed by specialized enzymes (RNA polymerases). RNA polymerases transcribe DNA with the formation of elongation complexes (EC), including those involved in transcription regulation. Cryo-electron microscopy (cryo-EM) allows us to determine the structures of these complexes and clarify the mechanisms of chromatin transcription. However, the preparation of EC samples suitable for cryo-EM study presents certain difficulties. In this study, the development of protocols for preparing EC samples with the location of RNAP active center at the position +39 from the nucleosome entrance (EC+39) was carried out. The formation of complexes was confirmed by the methods of electrophoresis and negative stain electron microscopy. The developed methods can be used for studying EC+39 using cryo-EM method.
Osina et al. (Mon,) studied this question.