INCREASED HALF-LIFE OF MU-IMMUNOGLOBULIN MESSENGER-RNA DURING MOUSE B-CELL DEVELOPMENT INCREASES ITS ABUNDANCE

When B cells encounter antigen, the cells mature into terminally differentiated plasma cells and the amount of steady-state immunoglobulin (Ig) μ mRNA is increased 23-60-fold over the amount seen in earlier B cell stages. Most of this dramatic increase in Ig gene mRNA accumulation could be due to post-transcriptional regulation. We have treated a series of mouse cell lines fixed at different stages of B cell differentiation with an adenosine nucleotide analog 5,6-dichloro-1-β-d-ribofuranosylbenzimidazole (DRB) which specifically blocks synthesis of new RNA polymerase II transcripts. The amount of μ heavy chain cytoplasmic RNA, measured by quantitative Northern blot analysis at various times post DRB treatment, is reflective of the transcript's stability. The μ mRNA half-life values observed from the earliest-stage lymphomas ( 70Z 3 and WEHI-231) are about 1.9-4 hr, whereas the t 1 2 of μ mRNA in the hybridomas (Hyb54.3C2 and IdG11) is about 13-17 hr. There is, therefore, a nine-fold maximal increase in half-life of the μmRNA in the Hyb54.3C2 over that observed in the earliest stage ( 70Z 3) cells. © 1990.