RNA processing is a limiting step for murine tumor necrosis factor beta expression in response to interleukin-2

We have previously reported that tumor necrosis factor beta (TNF beta) expression is induced by interleukin-2 (IL-2) in the murine lymphocytic T-cell line CTLL-2. In this study, we have characterized the nuclear and cytoplasmic TNF beta transcript and assessed their role in TNF beta gene expression. A unique feature of TNF beta expression was the accumulation of nuclear precursors, which reflected a slow nuclear RNA processing. As a consequence, there was a delay in the appearance of cytoplasmic messengers after the transcriptional induction of TNF beta by IL-2. We also found that two messengers, the fully spliced messenger and an intron 3-retaining messenger, were exported to the cytoplasm and actively translated. The same pattern of expression was observed in concanavalin A-stimulated splenocytes, although the level of expression was much lower than in CTLL-2 cells. The simple genetic structure and the high level of accumulation of nuclear precursors make TNF beta a particularly attractive model system to use for studies of RNA processing and cytoplasmic transport of partially spliced messengers.