Interactions And Biochemical Analysis Of The HSV-1 UL25 Capsid Protein With Cytoskeleton Microtubule Protein

Herpes Simplex Virus 1 (HSV-1) is a common pathogen, homo sapiens are its natural host. HSV-1 infects host through damaged skin or mucous membrane and proliferates in epithelial tissue. It even infects neurons from nerve terminal situated in epithelial tissue. After primary infection, the virus could establish latent infection at trige-minal ganglion and dorsal root ganglion etc.HSV-1 UL25 gene product is an essential capsid protein which locates on the external surface of virus capsid near the vertices. It is required for many crucial biological events during viral infection, including intracellular transport of virions,proliferation and assembling of virions in cell etc. Our research indicated UL25 gene product can interact with distinct structural and functional cell proteins by using yeast two-hybrid screening system. Cytoskeleton microtubule protein - tubulin was one of them.β-D-galactosidase activity assays demonstrated a specific interaction between UL25 and tubulin.UL25 was recombined into pEGFP-N2 to express UL25-EGFP fusion protein. Fluorescence experiment using the EGFP-UL25 fusion protein and an anti-cellular tubulin immunofluorescence antibody demonstrated that UL25 locates in cytoplasm and co-localizes with tubulin. Locations of UL25 were yet consistent with indiscriminate tubulins after treating cell with colchicine which can dissociate microtubule. These results indicate there are interactions between tubulin and UL25 in cell. Base on yeast two-hybrid screening and fluorescence analysis, it is possible that UL25 protein plays an essential role in transport of viral capsids owing to herpesviruses transport along microtubules in cell.Further fluorescence investigations with different fragment deletion mutants of the UL25 gene suggested that the locations of 135-353aa of UL25 and its carboxyl terminus 360-580aa were similar to UL25 protein, and the amino terminus 140aa of UL25 localized to cytoplasm(co-localized with tubulin), as well as to nucleus. Combining with results from yeast two-hybrid screening system that UL25 interacts with transcriptional and regulatory proteins such as eukaryotic translation elongation factor, we infer that UL25 involves in certain unknown functions in nucleus. It is possible the amino terminus is the significant domain of UL25 to interact with different cellular proteins.