Effects of sodium butyrate on the rearranged c-myc expression in mouse plasmacytoma cells.

The expression of c-myc mRNA was examined after 4 h of sodium butyrate treatment in a mouse plasmacytoma (MPC) cell line (S194). Steady-state levels of rearranged c-myc mRNA were suppressed by the agent in S194 cells. Run-on assay demonstrated that the suppression of the rearranged c-myc mRNA in the MPC was correlated with the transcriptional downregulation of the gene. The suppression was also accompanied by the reduced DNase I sensitivity of the gene. These findings suggest that the rapid downregulation of c-myc mRNA by sodium butyrate is subject to regulation at the transcriptional level following the alteration of the DNase I sensitive chromatin structure in mouse plasmacytoma cells.