The Latency-Related Gene of Bovine Herpesvirus 1 Inhibits Programmed Cell Death

Authors

Janice Ciacci-Zanella, University of Nebraska - Lincoln
Melissa Stone, University of Nebraska - Lincoln
Gail A. Henderson, University of Nebraska - LincolnFollow
Clinton J. Jones, University of Nebraska - LincolnFollow

Document Type

Article

Date of this Version

December 1999

Comments

Published in JOURNAL OF VIROLOGY, Dec. 1999, p. 9734–9740 Vol. 73, No. 12. Copyright © 1999, American Society for Microbiology. Used by permission.

Abstract

Although viral gene expression occurs in the peripheral nervous system during acute infection, bovine herpesvirus 1 (BHV-1) gene expression is extinguished, many neurons survive, and latency ensues. The only abundant viral transcript expressed during latency is the latency-related (LR) RNA, which is alternatively spliced in trigeminal ganglia during acute infection (L. Devireddy and C. Jones, J. Virol. 72:7294–7301, 1998). A subset of neurons express a protein encoded by the LR gene and the LR protein (LRP) is associated with cyclin-dependent kinase 2 (Cdk2)/cyclin complexes during productive infection (Y. Jiang, A. Hossain, M. T. Winkler, T. Holt, A. Doster, and C. Jones, J. Virol. 72:8133–8142, 1998). LR gene products inhibit cell cycle progression, perhaps as a result of LRP interacting with Cdk2/cyclin complexes. During acute infection, expression of cyclin A occurs in trigeminal ganglionic neurons (L. M. Schang, A. Hossain, and C. Jones, J. Virol. 70:3807–3814, 1996). Inappropriate expression of G₁- and S-phase cyclins can initiate programmed cell death (PCD), apoptosis, in neurons, suggesting that LR gene products inhibit PCD. To test this hypothesis, we modified an assay to measure PCD frequency in transiently transfected cells. C6-ceramide, fumonisin B1 (FB₁), or etoposide was used to initiate PCD following transfection of cells with plasmids expressing LR gene products and the β-galactosidase gene. Transfected cells that survived were quantified by counting β-galactosidase- positive cells. Plasmids that expressed LR gene products promoted survival of monkey kidney (CV-1), human lung (IMR-90), or mouse neuroblastoma (neuro-2A) cells after induction of PCD. Plasmids with termination codons at the beginning of LR open reading frames or deletion of sequences that mediate splicing of LR RNA did not promote cell survival following PCD induction. We hypothesize that LR gene products play a role in promoting survival of postmitotic neurons during acute infection or reactivation.