Understanding viruses is a key area of research for public health. There is still a lot that is not understood about how retroviruses replicate and infect host cells, leaving gaps in our understanding which if filled may lead to new retroviral drugs for treating these viral infections. Kate Bishop and her team at the Francis Crick institute London investigate many aspects of viral biology including HIV and one target of particular interest, the p12 from Murine Leukaemia Virus (MLV).
Dr Bishop enlisted the help of Cambridge Research Biochemicals to produce a custom antibody to this key target, MLV p12. Using this highly specific antibody there were able to further the understanding of many aspects of how p12 behaves.
MLV p12 is a cleavage product from the Gag protein and is essential for viral replication. The N-terminal domain of p12 binds directly to capsid (CA) and stabilises the mature viral core, whereas the C-terminal domain (CTD) may be involved in chromatin binding. Using their new, highly specific, custom made anti-p12 antibody from CRB in a series of immuno-localisation and immunoblotting assays the team at The Frances Crick Institute characterised the interactions of p12 with both viral and host proteins and were able to show that p12 can act as a tether between viral pre integration complexes (PICs) containing capsid (CA) and mitotic chromatin by directly binding both hexameric CA and nucleosomal histone proteins. By tethering the CA-containing PIC to mitotic chromatin, p12 may influence global nuclear targeting of MLV integration.
The anti-MLV p12 antibody is available to buy from our Discovery Antibodies Catalogue
Kate Bishop and her team used these results to propose a model for p12 function: Following Gag cleavage, p12 binds to the hexameric CA lattice via its N-terminal domain, stabilising the viral core and causing a change in the conformation of p12 increasing the affinity of p12 for nucleosomes. Upon breakdown of the nuclear envelope in mitosis, the PIC is targeted to condensed chromatin by CA-bound, phosphorylated p12. Following exit from mitosis, either dephosphorylation of p12 or chromatin decondensation could reduce the affinity or avidity of the interaction and cause p12 to be released from chromatin.
Citation:
Wanaguru et al., (2018). Murine leukemia virus p12 tethers the capsid-containing pre-integration complex to chromatin by binding directly to host nucleosomes in mitosis. PLoS Pathog. 14(6): e1007117. https://doi.org/10.1371/journal.ppat.1007117