A 6-fold difference in the half-life of immunoglobulin mu heavy chain mRNA in cell lines representing two stages of B cell differentiation.

When B cells differentiate into plasma cells, there is a large increase in the cellular content of mRNA coding for immunoglobulin. This increase cannot be fully accounted for by the increase in rate of transcription of the genes. We have investigated the possibility that the half-life of mu heavy chain mRNA increases during B cell differentiation, by measuring the rates of decay of the same endogenous mu gene in two cell lines representing the B cell and the plasma cell. Using a pulse-chase protocol, it was found that there was a significant increase in the half-life of mu mRNA between the B cell and the plasma cell, and no detectable difference in the average half-life of total poly(A)+ RNA in the two cell lines. The reduced rate of decay of mu mRNA in the more differentiated cell type is almost sufficient to account for the difference in steady state mu mRNA levels between the two cell lines.