A role for Z-DNA binding in vaccinia virus pathogenesis

Abstract

The N-terminal domain of the E3L protein of vaccinia virus has sequence similarity to a family of Z-DNA binding proteins of defined three-dimensional structure and it is necessary for pathogenicity in mice. When other Z-DNA-binding domains are substituted for the similar E3L domain, the virus retains its lethality after intracranial inoculation. Mutations decreasing Z-DNA binding in the chimera correlate with decreases in viral pathogenicity, as do analogous mutations in wild-type E3L. A chimeric virus incorporating a related protein that does not bind Z-DNA is not pathogenic, but a mutation that creates Z-DNA binding makes a lethal virus. The ability to bind the Z conformation is thus essential to E3L activity. This finding may allow the design of a class of antiviral agents, including agents against variola (smallpox), which has an almost identical E3L.

Biological function of the vaccinia virus Z-DNA-binding protein E3L: Gene transactivation and antiapoptotic activity in HeLa cells

“…Likewise, Tyr 177 of Z␣ ADAR1 forms an important interaction in Z-DNA binding, and mutating it to Ala strongly decreases Z-DNA binding (Fig. 1B) (8). When the analogous Tyr 48 of E3L is mutated to Ala (Y48A E3L) due to loss of an important van der Waals contact and a hydrogen bond, the activation activity of E3L is strongly decreased.…”

“…Although E3L accumulates in the nucleus, consistent with previous reports (3,11), its function there is unknown. It has been demonstrated that the E3L N-terminal domain binding to Z-DNA is necessary for pathogenicity in mice (8). Z-DNA-forming sequences are found near the transcription start site of many human genes (14), and negative supercoiling generated behind a moving polymerase during transcription (15) stabilizes Z-DNA formation.…”

“…The ability to recognize the Z-DNA conformation is essential for E3L function (8), and mutations in chimeric and wild-type E3L of VV that decrease Z-DNA binding were found to have decreased viral pathogenicity (8). When Pro 63 of wild-type E3L [analogous to Pro 192 of Z␣ ADAR1 (Fig.…”

“…Both N-terminal and C-terminal domains are required for infection and full pathogenesis in the mouse model (2). It has been shown that viral pathogenicity requires E3L binding to Z-DNA (8). The N-terminal half of the E3L protein is highly conserved among distantly related poxviruses, and E3L from another poxvirus has been cocrystallized with Z-DNA (9), but the functional role of this region has not been well characterized.…”

“…The N-terminal half of the E3L protein is highly conserved among distantly related poxviruses, and E3L from another poxvirus has been cocrystallized with Z-DNA (9), but the functional role of this region has not been well characterized. It has been suggested that the N-terminal domain of E3L is involved in the direct inhibition of protein kinase R (PKR) activation, nuclear localization, and Z-DNA binding (8,10,11). A VV mutant lacking E3L induces apoptosis in HeLa cells (12).…”