VIRAL-INFECTION .1. REGULATION OF PROTEIN-SYNTHESIS DURING VACCINIA VIRAL-INFECTION OF ANIMAL-CELLS

Regulation of vaccinia viral infection was studied using three animal cell. lines: KRC-7 (rat hepatoma), L929 (mouse fibroblast), and CV-1 ( African green monkey kidney). KRC-7 is highly enriched in p67, a glyco protein which protects eIF-2 alpha-subunit from phosphorylation by eIF -2 kinases. We report: (i) At 5 pfu per cell of the virus, KRC-7 is re sistant to the virus. Other cells are sensitive. At 25 pfu per cell of the virus, KRC-7 is also sensitive to the virus. After productive vir al infection, the cell extracts showed strong p67-DG activity and acti vely deglycosylated exogenous p67. After p67-deglycosylation, the cell extracts also phosphorylated eIF-2. (ii) The rate of synthesis of a m ajor host protein (similar to 45 kDa) in infected L929 cells measured after 2 h of viral infection declined more than 50%. The rate declined thereafter, The rate of synthesis of host proteins in viral-resistant KRC-7 cells (infected with 5 pfu per cell of the virus) remained unch anged. The mechanism of resistance of KRC7 cells to vacinia virus at 5 pfu per cell of the virus was investigated, The p67 level in these ce lls was varied by growing the cells under different physiological cond itions such as serum starvation and expression of p67-sense and p67-an tisense DNA. At low p67 level in the cells, p67-DG is activated. This deglycosylates p67 and inactivates p67. This accompanies eIF-2 phospho rylation and shutoff of host protein synthesis, At high p67 level in t he cells, activation of p67-DG is prevented. This prevents shutoff of host protein synthesis and viral growth. (C) 1997 Academic Press.