12:00noon Tuesday 8th October
Room 208, 2nd floor,
Microbiology building,
720 Cumberland Street
Jan Webber
Head of the Virology Research-Service Team, Institute of Organic Chemistry & Biochemistry of the Czech Academy of Sciences
‘Arginine methylation and ubiquitination of hepatitis B virus core protein’
Post-translational arginine methylation and ubiquitination is responsible for regulation of many biological processes. In mammals, protein arginine methyltransferase 5 (PRMT5), is the main enzyme responsible for majority of mono- and symmetric dimethylation of arginine that is critical for genome organisation, transcription, and membrane trafficking. Likewise, modification of viral proteins by ubiquitin and ubiquitin-like modifiers have been shown to be critical for their stability, intracellular localisation and function. We have recently identified, PRMT5, as a novel and effective regulator of hepatitis B virus (HBV) RNA transcription and replication. We also found that PRMT5 interacted with the HBV core protein (HBc) and dimethylated arginine residues within the arginine-rich domain of the carboxyl-terminus. The HBc symmetric dimethylation appeared to be linked to serine phosphorylation and nuclear import of HBc protein. Conversely, the monomethylated HBc retained in the cytoplasm. Mass spectrometry analysis of HBc identified next to the arginine methylation and phosphorylation sites that HBc can be predominantly mono-ubiquitinated in cells and recognized several lysine/serine/threonine residues that could potentially be modified by ubiquitination or ubiquitin-like modification. We further analysed ubiquitination and other ubiquitin-like modification of HBc protein such as sumoylation, neddylation, and ISGylation by series of immunoprecipitation experiments. Finally, we characterised HBc ubiquitination using HBc-Lys-to-Arg mutants with a series of different ubiquitin variants as well as wild type ubiquitin. In summary, we identified PRMT5 as a potent restriction factor of HBV replication which may control HBc cell trafficking and function and described two novel types of HBc post-translational modifications, arginine methylation and ubiquitination.
