What happens if the RNA polymerase malfunctions

Deciphered 3D structure of RNA polymerase III

research results

The enzyme RNA polymerase III (Pol III) occurs in all higher organisms and enables certain sequences of the genetic blueprint of a cell to be translated into RNA. In the cell, Pol III is an essential factor for growth and survival; malfunctions can trigger certain tumor or hereditary diseases. In order to better understand Pol III functionally and to determine its structure at the molecular level, the working groups headed by Prof. Dr. Alessandro Vannini at the Institute of Cancer Research in London and Prof. Dr. Christoph Engel at the University of Regensburg. The results have now been published in the journal Nature Communications.

The first hurdle to be overcome by the participating scientists was to isolate a sufficient amount of intact protein of the human Pol III complex consisting of 17 subunits. For this purpose, cell lines in laboratory culture were modified using the CRISPR / Cas9 method and used in large quantities. The functional biochemical investigation of the purified polymerase showed that the isolated enzyme is still able to carry out its important cellular functions, i.e. to transcribe DNA into RNA. In addition, the authors used an integrative structural biology approach and combined the methods of single-particle cryo-electron microscopy, X-ray crystallography and other techniques to decipher the structure of the human Pol III.
The results obtained confirmed a presumption that many features of Pol III are similar in all higher organisms. The human enzyme, however, has peculiarities, the function of which can now be analyzed in addition to the structural investigation using cell biological experiments. It turned out that these peculiarities play a decisive role in the structure and stability of the enzyme. Based on these and other findings, it is assumed that this protein part could play an important role in the regulation of the entire enzyme through various environmental influences with which human cells can be confronted.

With the aid of the structural information about this enzyme, known mutations that occur in various diseases could also be precisely localized in the 3D structure. Neurodegenerative diseases such as Treacher-Collins syndrome can be attributed to mutations in the Pol III complex. The studies showed that these changes lead to reduced enzyme stability, which explains serious consequences for the cells and the entire organism. Other Pol III mutations, which trigger hypersensitivity to viral infections, have, however, been found at various points on the surface of the enzyme. It is assumed that these peripheral mutations mainly negatively influence the identification of viral DNA in the cell plasma.
The results of the research team led by Professor Engel and Professor Vannini show at which point in the 3D structure of the human Pol III enzyme the mutations responsible for certain diseases occur. The authors succeeded in creating a kind of map with the help of which new treatment options for tumor diseases could be developed.

Scientific contact:
Prof. Dr. Christoph Engel
University of Regensburg
Regensburg Center for Biochemistry
Telephone 0941 943-2718 / -2809
Email: [email protected]

Original publication:
E. Ramsay, G. Abascal-Palacios, J. Daiß, H. King, J. Gouge, M. Pilsl, F. Beuron, E. Morris, P. Gunkel, C. Engel, A. Vannini, “Structure of human RNA Polymerase III ”, Nature Communications (2020)
DOI: https://doi.org/10.1038/s41467-020-20262-5