p67, a cellular glycoprotein, protects eIF2alpha from phosphorylation by inhibitory kinases such as double-stranded RNA dependent eIF2 kinase, PKR, and heme-controlled repressor and thus promotes protein synthesis in mammalian cells. To investigate whether p67 is essential for the survival of mammalian cells, the basal level of p67 was lowered from rat tumor hepatoma cells using antisense approach. The antisense p67 RNA specifically lowered the levels of p67 message and the protein from these cells. As a result, the level of eIF2alpha phosphorylation increased significantly, the overall rate of protein synthesis decreased, and the rate of DNA synthesis also decreased in mammalian cells with low levels of p67 as compared to that seen in control cells. In addition, the majority of the cells with low levels of p67 are arrested at the G1 phase of the cell cycle and die with apoptosis. Taken together, these results suggest that appropriate levels of p67 is required for normal growth of mammalian cells.
Copyright 1999 Academic Press.