ENDOGENOUS BUTYRYLCHOLINESTERASE IN SV40-TRANSFORMED CELL-LINES - COS-1, COS-7, MRC-5 SV40, AND WI-38 VA13

Comparison of proteins expressed by SV40 transformed cell lines and un transformed cell lines is of interest because SV40 transformed cells a re immortal, whereas untransformed cells senesce after about 50 doubli ngs. In MRC-5 SV40 cells, only seven proteins have previously been rep orted to shift from undetectable to detectable after transformation by SV40 virus. We report that butyrylcholinesterase is an 8th protein in this category. Butyrylcholinesterase activity in transformed MRC-5 SV 40 cells increased at least 150-fold over its undetectable level in MR C-5 parental cells. Other SV40 transformed cell lines, including COS-1 , COS-7, and WI-38 VA13, also expressed endogenous butyrylcholinestera se, whereas the parental, untransformed cell lines, CV-1 and WI-38, ha d no detectable butyrylcholinesterase activity or mRNA. Infection of C V-1 cells by SV40 virus did not result in expression of butyrylcholine sterase, showing that the butyrylcholinesterase promoter was not activ ated by tile large T antigen of SV40. We conclude that butyrylcholines terase expression resulted from events related to cell immortalization and did not result from activation by the large T antigen.