The MLV p12 protein is essential for both early and late stages of viral replication. We are studying the function of p12 during early, post-entry replication.
All retroviral genomes contain a gag gene that codes for the Gag polyprotein. Gag is cleaved upon viral maturation to release individual proteins, including matrix, capsid and nucleocapsid, providing the structural components of the virion. In murine leukaemia virus (MLV), Gag cleavage releases an additional protein, named p12, required for both early and late stages of the viral life cycle. We are characterising the role of p12 during early events. Viruses carrying mutations in p12 are able to reverse transcribe their genomes but cannot integrate this nascent DNA.
Using mutagenesis studies combined with microscopy and biochemical experiments, we mapped two functional domains in p12. We showed that the N-terminal motif of p12 binds directly to the capsid protein and that mutations in this motif affect the structure and stability of the viral capsid shell.
Additionally, we have demonstrated that p12 is involved in directing the viral pre-integration complex to chromatin ready for integration. We are continuing to use p12 to unravel the key processes of capsid shell formation and break down (uncoating) and chromatin tethering, all of which are required for all retroviral infections.