Name: Suzanne Rose

Email: suzannerose@alltel.net

Author: Suzanne L. Rose1, Ming Kang2, James L. Van Etten2,3

Author affiliation: 1. School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE USA *Presenting author 2. Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE USA 3. Department of Plant Pathology; NebraskaCenter of Virology, University of Nebraska-Lincoln, Lincoln, NE USA

Abstract title: Viral-host interactions of PBCV-1 and Chlorella nc64a in viral DNA packaging

Absstract:

Paramecium bursaria chlorella virus-1 (PBCV-1) is the type member of the Phycodnaviridae family. PBCV-1 is a lytic, dsDNA virus with a 330-Kb genome that encodes ~365 proteins. Its host, Chlorella NC64A, is a unicellular eukaryotic green alga. The life cycle of PBCV-1 is about 8 hours, with DNA synthesis starting at 60-90 minutes post infection. Virus assembly centers can be seen in electron micrographs at 2-5 hours post infection followed by localized lysis and release of infectious progeny. Programmed cell death is a known host response to viral infection. The host cell death pathway involves the activation of a family of caspases. Bioinformatic studies demonstrated that the virus encoded gene A392R has a conserved caspase cleavage site that is a conserved core sequence among all nucleocytoplasmic large DNA viruses (NCLDV). Cleavage of the expressed viral protein A392R with a commercial metacaspase resulted in two cleavage products, of the predicted size, supporting the hypothesis of cleavage at the conserved site. The resulting subunits of A392R cleavage have putative functions as a portal protein and ATPase motor, both predicted to function in viral DNA packaging. Preliminary studies indicate that addition of caspase inhibitors reduces infectious progeny release by ~90%. The data suggest a dependent viral-host interaction. Further studies will include determining the structure and function of the polypeptide cleavage products.