CHANGES IN ABUNDANCE OF IGG 2A MESSENGER-RNA IN THE NUCLEUS AND CYTOPLASM OF A MURINE B-LYMPHOMA BEFORE AND AFTER FUSION TO A MYELOMA CELL

Changes in IgG mRNA half-life, transcription and nuclear and cytoplasm ic abundance were studied in two cell lines which contain an identical Ig gamma 2a heavy chain but which differ in its expression. The A20.2 J mouse lymphoma expresses about equal amounts of Ig gamma 2a secretor y- and membrane-specific mRNAs whereas in the AXJ hybrids, resulting f rom the fusion of A20.2J with the J558L myeloma, the secretory-specifi c form dominates. Further evidence of dominance of the myeloma phenoty pe was seen in the large changes in mRNA abundance and nuclear accumul ation as well as in a small increase in Ig gamma 2a mRNA half-lives fo r both secretory and membrane forms. Contributing to the observed >100 -fold increase in the ratio of secretory vs membrane forms of the Ig g amma 2a heavy chain in the AXJ hybrids are both a 10-fold decrease in the production of the membrane form by post-transcriptional RNA proces sing events and a approximate to 6-7-fold decrease in the nuclear to c ytoplasmic ratio for the Ig secretory gamma 2a and kappa light chain R NAs. Differential RNA accumulation in the nucleus in the lymphoma cell therefore contributes to the differential expression of Ig secretory mRNA. Copyright (C) 1996 Elsevier Science Ltd.