Role of Z DNA binding in vaccinia virus pathogenesis

Role Z-DNA Binding Vaccinia Virus Pathogensis

The work of Yang-Gyun Kim, et al. entitled "A Role for Z-DNA Binding in Vaccinia Virus Pathogenesis" (2003) reports a study on Vaccinia, reported to be a poxvirus that contains DNA with less than 200 genes and which undergoes replication in infected cells and specifically in the cytoplasm. When a strain adapted from vaccinia was given to a mouse, the mouse died in less than one week stated to be dependent upon the route of infection and dosage given to the mouse. Kim, et al. (2003) reports that the viral E3L gene product "has been extensively characterized and is essential for virulence." A 25-kDa protein is encoded by E3L and is stated to have to primary domains: (1) an N-terminal domain with a sequence that is comparable to the vertebrate Zol family of Z-DNA-binding domains; and (2) a C-terminal domain with a typical double-stranded RNA binding motif. (Kim, et al., 2003)

The study reported involved d (CG)6 being converted from right-handed B-DNA to left-handed Z-DNA, which was monitored through taking measurement of changes that occurred in CD in the UV as well as measuring the rate, and extent of the protein conversion by the Zol ADAR1 of d (CG)6 from B-DNA to Z-DNA, which was measured. Purification was performed on the proteins utilized in the CD studies.

Results of the study demonstrated that virulence requires N-terminal residues of E3L. In the case that the first 83 residues are deleted and only the C. terminus of E2L is left, the pathogenicity in mice decreased dramatically. In order that an examination of Z-DNA binding be conducted a domain swap was performed which replaced 67 N-terminal amino acids of E3L being replaced by 64 residues of Zol ADAR1. Less than 50 residues are reported to have been altered. 14 identical residues remained stated to be inclusive of those that "contact Z-DNA in the Zol ADAR1 crystal structure. Retained by the chimeric virus was the "wild-type C-terminal E3L domain. Incranial injection into mice was used to test the construct for the purpose of assaying pathogenicity with an exchange of 67 amino acids from Zol DLM1. 12 residues are reported to have remained the same and this includes the residues that bind to Z-DNA. The Zol DLM1-D3Lc chimera was found to be completely pathogenic resulting in only a few essential residues with the domain of the N-terminal of E3L being enough for biological activity when measuring for lethality. In mutations that result in the weakening of Z-DNA, binding it was demonstrated that this results in a loss of pathogenicity and virus virulence, which ultimately results in functional loss. Vaccinia E3L is reported to have been "implicated in at least four possible roles which are key for viral pathogenesis: (1) Z-DNA binding; (2) nuclear localization; (3) IFN-blocking activities; and (4) higher-order oligomerization. (Kim, et al., 2003)