INCREASED RATE OF TRANSCRIPTION CONTRIBUTES TO ELEVATED EXPRESSION OFTHE MUTANT P53 GENE IN BURKITTS-LYMPHOMA CELL

Mutations and elevated levels of the p53 tumor suppressor protein have been reported in Burkitt's lymphomas (BL). We investigated whether el evated levels of the mutant p53 protein can be due to transcriptional or posttranscriptional mechanisms. In surveying a series of B-lymphoid cell lines, we found that a high level of the p53 protein tended to r eflect high steady-state levels of p53 mRNA, p53 mRNA exhibited high s tability in all of the cells tested, Cycloheximide treatment of the ce lls showed that the low level of p53 mRNA in non-BL lymphoid cells can not he attributed to posttranscriptional regulation bg a labile prote in, Nuclear run-on experiments revealed that the transcription rate of the p53 gene is about four times higher in some high p53-expressing B L cell lines as compared to low p53-expressing lymphoid cell lines. Ou r data suggest that an increase in the rate of transcription of the p5 3 gene is one of the mechanisms that contribute to elevated levels of mutant p53 protein observed in many tumor cells.