THE SIMIAN-VIRUS-40 LARGE T-ANTIGEN DOES NOT INHIBIT TRANSLATION OF THE 14-KDA MYELIN BASIC-PROTEIN MESSENGER-RNA IN RETICULOCYTE LYSATES OR IN TRANSFECTED CELLS

Viral T antigens are transcription factors that have been suspected of inhibiting expression of the myelin basic protein (MBP) mRNA at the t ranslational level in vitro and in vivo. The effect of simian virus 40 (SV40) large T antigen (T-ag) was examined on the translation of the 14-kDa MBP mRNA in reticulocyte lysates and on MBP expression after tr ansfection into cells that express SV40 T-ag. SV40 T-ag did not inhibi t translation of 14-kDa MBP cRNAs in cell-free translations even at 30 mu M (similar to 600 mu g/ml) T-ag. Permanent transfection of COS-1 c ells (which endogenously express SV40 T-ag) with the 14-kDa MBP cDNA r esulted in the expression of the 14-kDa MBP as determined by western b lot analysis. Permanent transfection of N20.1 cells, an oligodendrocyt e line immortalized with a temperature-sensitive SV40 T-ag, with the 1 4-kDa MBP cDNA construct also resulted in the expression of the 14-kDa MBP under conditions in which the cells expressed functional SV40 T-a g. These results indicate that SV40 T-ag does not prevent expression o f the MBP gene at the translational level and that in those immortaliz ed oligodendrocyte lines that express MBP mRNA, but not MBP protein, s ome factor other than the SV40 large T-ag is responsible for the postt ranscriptional regulation.