The highly inducible member of the 70 kDa family of heat shock proteins increases canine distemper virus polymerase activity.
The cellular stress response is characterized by the production of heat shock proteins (HSP) which serve important cytoprotective functions. Paradoxically, in vitro induction of the stress response promotes cytopathic effect mediated by infection with canine distemper virus (CDV). The stress-mediated increase in cytopathic effect is correlated to the formation of complexes between the viral nucleocapsid (NC) and the major inducible member of the approximately 70 kDa family of HSP (hsp72). The objective of the present study was to document the functional significance of CDV NC-HSP interaction. Cytoplasmic NC was purified from Vero cells lytically infected with the Onderstepoort strain of CDV. Both ultrastructural variants of CDV NC interacted with both hsp72 and the constitutively expressed member of the approximately 70 kDa family of HSP (hsp73) in a reversible and ATP-dependent manner. An effect of hsp72/73 on NC polymerase activity was demonstrated using cell-free assays derived from either Vero or HeLa cell lines. Antibody specific to hsp72 suppressed both basal and stress-enhanced polymerase activity whereas hsp73-specific antibody had no affect. Supplementation of purified hsp72/73, but not hsp73 alone, enhanced basal polymerase activity in a dosage-dependent manner. Using purified NC variants, polymerase activity was demonstrated in pre-formed hsp72/73-NC complexes but not in NC devoid of HSP. These results suggest that the stimulatory effect of the stress response upon CDV gene expression may, in part, be mediated by a reversible and direct interaction between hsp72 and the viral core particle.
Oglesbee
M J
MJ
Department of Veterinary Biosciences, Ohio State University, Columbus 43210, USA. oglesbee.1@osu.edu
Liu
Z
Z
Kenney
H
H
Brooks
C L
CL
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002522:Chlorocebus aethiops; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004217:Distemper Virus, Canine / Q000201:enzymology*; D004285:Dogs; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis* / Q000276:immunology; D006367:HeLa Cells; D006801:Humans; D019251:Nucleocapsid / Q000378:metabolism; D014709:Vero Cells; D014764:Viral Proteins / Q000378:metabolism*
D018840:HSP70 Heat-Shock Proteins; D014764:Viral Proteins; D000255:Adenosine Triphosphate; D012321:DNA-Directed RNA Polymerases