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Conservation of L and 3C proteinase activities across distantly related aphthoviruses
Tracey M Hinton1, Natalie Ross-Smith2, Simone Warner1
1Department of Microbiology and Immunology and the Co-operative Research Centre for Vaccine Technology, The University of Melbourne, Victoria 3010, Australia1.
Abstract:
The foot-and-mouth disease virus (FMDV) leader (L) proteinase is an important virulence determinant in FMDV infections. It possesses two distinct catalytic activities: (i) C-terminal processing at the L/VP4 junction; and (ii) induction of the cleavage of translation initiation factor eIF4G, an event that inhibits cap-dependent translation in infected cells. The only other member of the Aphthovirus genus, equine rhinitis A virus (ERAV), also encodes an L protein, but this shares only 32% amino acid identity with its FMDV counterpart. Another more distantly related picornavirus, equine rhinitis B virus (ERBV), which is not classified as an aphthovirus, also encodes an L protein. Using in vitro transcription and translation analysis, we have shown that both ERAV and ERBV L proteins have C-terminal processing activity. Furthermore, expression of ERAV L, but not ERBV L, in BHK-21 cells resulted in the efficient inhibition of cap-dependent translation in these cells. We have shown that the ERAV and FMDV L proteinases induce cleavage of eIF4GI at very similar or identical positions. Interestingly, ERAV 3C also induces eIF4GI cleavage and again produces distinct products that co-migrate with those induced by FMDV 3C. The ERBV L proteinase does not induce eIF4GI cleavage, consistent with its inability to shut down cap-dependent translation. We have also shown that another unique feature of FMDV L, the stimulation of enterovirus internal ribosome entry site (IRES) activity, is also shared by the ERAV L proteinase but not by ERBV L. The functional conservation of the divergent ERAV and FMDV proteinases indicates the likelihood of a similar and important role for these enzymes in the pathogenesis of infections caused by these distantly related aphthoviruses.
Insights
The foot-and-mouth disease virus (FMDV) L proteinase and equine rhinitis A virus (ERAV) L protein share critical functions in viral pathogenesis, including inhibiting host cell translation. These findings highlight conserved virulence mechanisms in related aphthoviruses.
Area of Science:
- Virology
- Molecular Biology
- Biochemistry
Background:
- The foot-and-mouth disease virus (FMDV) leader (L) proteinase is a key virulence factor.
- FMDV L proteinase has C-terminal processing and eIF4G cleavage activities, inhibiting host translation.
- Equine rhinitis A virus (ERAV) and equine rhinitis B virus (ERBV) also encode L proteins with varying homology to FMDV L.
Purpose of the Study:
- To investigate the functional conservation of L proteinases from different aphthoviruses, specifically FMDV, ERAV, and ERBV.
- To compare the catalytic activities and effects on host cell translation of these viral L proteins.
Main Methods:
- In vitro transcription and translation assays were used to analyze L protein activities.
- Expression of viral L proteins in BHK-21 cells assessed their impact on cap-dependent translation.
- Analysis of eIF4GI cleavage products and enterovirus internal ribosome entry site (IRES) activity.
Main Results:
- Both ERAV and ERBV L proteins exhibit C-terminal processing activity.
- ERAV L protein, but not ERBV L, efficiently inhibited cap-dependent translation in BHK-21 cells.
- ERAV and FMDV L proteinases induce cleavage of eIF4GI at similar positions, and ERAV L shares FMDV L's ability to stimulate enterovirus IRES activity.
Conclusions:
- The L proteinases of FMDV and ERAV share significant functional conservation, particularly in their roles in inhibiting host translation and stimulating IRES activity.
- These conserved functions suggest a similar and crucial role for these enzymes in the pathogenesis of infections caused by these aphthoviruses.
- The findings underscore the importance of L proteinase functional conservation in aphthovirus evolution and virulence.