Redistribution of demethylated RNA helicase A during foot-and-mouth disease virus infection: role of Jumonji C-domain containing protein 6 in RHA demethylation

Previously, RNA helicase A (RHA) re-localization from the nucleus to the cytoplasm in foot-and-mouth disease virus (FMDV) infected cells was shown to coincide with loss of RHA methylated arginine residues at its C-terminus. The potential interaction between RHA and Jumonji C-domain (JmjC) protein 6 (JMJD6) arginine demethylase in infected cells was investigated. Treatment with N-oxalylglycine (NOG) inhibitor of JmjC demethylases prevented FMDV-induced RHA demethylation and re-localization, and also decreased viral protein synthesis and virus titers. Physical interaction between JMJD6 and RHA was demonstrated via reciprocal co-immunoprecipitation, where RHA preferentially bound JMJD6 monomers. Nuclear efflux of demethylated RHA (DM-RHA) coincided with nuclear influx of JMJD6, which was not observed using another picornavirus. A modified biochemical assay demonstrated JMJD6 induced dose-dependent demethylation of RHA and two RHA-derived isoforms, which could be inhibited by NOG. We propose a role for JMJD6 in RHA demethylation stimulated by FMDV, that appears to facilitate virus replication.

Foot and mouth disease leader protease (Lbpro): Investigation of prime side specificity allows the synthesis of a potent inhibitor

Foot and mouth disease virus expresses its genetic information as a single polyprotein that is translated from the single-stranded RNA genome. Proteinases contained within the polyprotein then generate the mature viral proteins. The leader protease (Lb(pro)) performs the initial cleavage by freeing itself from the growing polypeptide chain; subsequently, Lb(pro) cleaves the two homologues of the host cell protein eukaryotic initiation factor 4G (eIF4G). We showed that Lb(pro) possesses specific binding sites at the non prime side from S(1) down to S(7) [Santos et al. (2009) Biochemistry, 48, 7948-7958]. Here, we demonstrate that Lb(pro) has high prime side specificity at least down to the S'(5) site. Lb(pro) is thus not only one of the smallest papain-like cysteine peptidases but also one of the most specific. It can still however cleave between both K↓G and G↓R pairs. We further determined the two-step irreversible inhibition (E + I ↔ EI→ E - I) kinetic parameters of two known irreversible epoxide-based inhibitors of cysteine proteinases, E64 and CA074 on Lb(pro) that show for the reversible step (E + I ↔ EI) K(i) = 3.4 μM and 11.6 μM, and for the irreversible step (EI→E-I) k(4) = 0.16 and 0.06 min(-1), respectively. Knowledge of the Lb(pro) specificity led us to extend E64 by addition of the dipeptide R-P. This compound, termed E64-R-P-NH(2), irreversibly inhibited Lb(pro) with a K(i) = 30 nM and k(4) = 0.01 min(-1) and can serve as the basis for design of specific inhibitors of FMDV replication.

Structural analysis of foot-and-mouth disease virus 3C protease: a viable target for antiviral drugs?

Foot-and-mouth disease virus causes a major global agricultural problem that is difficult to control with existing vaccines. Structural analyses of the viral 3C protease not only have provided fresh insights into the catalytic mechanism of an unusual class of chymotrypsin-like cysteine proteases, but also are generating valuable information to drive the quest for effective antiviral therapies.

Foot-and-mouth disease virus 3C protease: recent structural and functional insights into an antiviral target

The 3C protease from foot-and-mouth disease virus (FMDV 3C(pro)) is critical for viral pathogenesis, having vital roles in both the processing of the polyprotein precursor and RNA replication. Although recent structural and functional studies have revealed new insights into the mechanism and function of the enzyme, key questions remain that must be addressed before the potential of FMDV 3C(pro) as an antiviral drug target can be realised.

Expression of the aphthovirus RNA polymerase gene in Escherichia coli and its use together with other bioengineered nonstructural antigens in detection of late persistent infections

A plasmid has been constructed containing the DNA sequences that direct the expression of the aphthovirus RNA-dependent RNA polymerase (virus infection-associated antigen, VIAA) in its native form. The aphthovirus polypeptide was designed to contain only a single additional amino acid, the N-terminal methionine. The recombinant protein has been purified and used in enzyme-linked immunoelectrotransfer blots to detect aphthovirus-specific antibodies in the sera of persistently infected animals. Furthermore, studies were carried out to test the hypothesis that antibodies against other nonstructural antigens appear in the sera of these animals. It was established that antibodies against polypeptides 3A and 3B can serve as complementary markers for late aphthovirus-carrier state detection. The considerable potential of this approach to detect aphthovirus-specific antibodies, when the isolation of infectious virus is not possible, was demonstrated. Negative results were obtained in animals from virus-free areas and in vaccinated cattle. This assay has the added advantage that no infectious or noninfectious virus is involved during antigen production.

Association of foot-and-mouth disease virus induced RNA polymerase with host cell organelles

The localization of foot-and-mouth disease viral-induced RNA polymerase has been determined in situ and in partially fractionated cell components by using polymerase antisera tagged with either peroxidase or ferritin. Electron microscopic examination revealed the polymerase to be heavily concentrated on membranes of the smooth membranous vacuoles (SMV) which are newly formed during infection and which were previously shown to be the site where newly synthesized viral RNA appeared. Polymerase antigen was also seen to be associated with the endoplasmic reticulum (ER), the assumed site of original synthesis, and to a lesser extent with mitochondria and the Golgi apparatus. There was no significant polymerase attachment to nuclear and plasma membranes.