Monday 19 August, 1:00pm
Biochemistry Seminar Room BIG13
Dr Alice McSweeney
Department of Microbiology and Immunology
Enzymatic Characterisation of the Human Norovirus ProPol Precursor Protein
Human norovirus (HuNV) is a leading cause of acute gastroenteritis worldwide with no approved vaccines or antiviral treatments. Replication of HuNV produces both precursor and mature proteins to generate multiple functionalities from the same sequence. One such precursor is ProPol, a multi-functional enzyme comprised of the norovirus protease and polymerase proteins and possessing both enzymatic activities. In addition, ProPol is the enzyme form that catalyses a nucleotidylylation reaction to covalently link a nucleotide monophosphate (NMP) to the viral protein VPg, an essential step for viral genome replication.
This seminar will present data on the three enzymatic activities of HuNV ProPol. I will briefly describe the protease activity and present characterisation of the de novo polymerase activity of the HuNV precursor ProPol and mature polymerase. This shows that enzymatic efficiencies of ProPol for RNA templates and ribonucleotides are equal or superior to those of mature Pol. In addition, I will compare the responses of the precursor and mature forms of these enzymes to potential antivirals.
Finally, I will describe the development of a nucleotidylylation assay that can be used to further characterise the addition of NMP to VPg. Using this assay, we show that non-nucleoside inhibitors can decrease nucleotidylylation. Surprisingly however, nucleoside inhibitors, which prevent polymerase activity, do not decrease nucleotidylylation nor were they used as a substrate for the reaction.
This study provides evidence that HuNV ProPol possesses overlapping and unique enzyme properties compared to mature Pol and will aid our understanding of the replication cycle of the virus and offers a new viral target for the development of antivirals.
