IPEB TRANSCRIPTION FACTOR REGULATING THE INTRACISTERNAL A-PARTICLE GENE DURING F9 CELL-DIFFERENTIATION IS EXPRESSED AT SITES OF LYMPHOID DEVELOPMENT

The murine intracisternal A particle (IAP) proviral elements are expre ssed at low levels in undifferentiated F9 embryonal carcinoma cells bu t are highly expressed when F9 cells are induced to differentiate into parietal endoderm-like cells. IAP elements are also expressed in pari etal endoderm-like PYS-2 cells. We previously identified an IAP proxim al enhancer (IPE) element that mediates a F9 differentiation-specific enhancer activity. We also identified a 60 kDa IPE binding (IPEB) prot ein whose activity is high in PYS-2 cells, where IAP is expressed, but very low in F9 cells. Transcription of IAP elements has also been sho wn in the adult mouse thymus and in activated splenic B cells. We have now shown by DNA affinity chromatography, sodium dodecyl sulfate-poly acrylamide gel electrophoresis, and band-shift analysis that the 60 kD a IPEB is expressed in adult T lymphocytes and in resting as well as l ipopolysaccharide activated splenic B cells but not in adult liver cel ls, suggesting an important role for IPEB in IAP transcription in vivo . In addition, we find IPEB expressed in the fetal mouse at sites of l ymphoid development, such as the liver, spleen, and thymus, suggesting it may play an important role in gene expression during lymphoid deve lopment. In support of this, we find IPEB in the human T cell tumor li nes, Jurkat and Molt 13, as well as the Daudi B cell line and in the n ormal calf thymus and in the thymus and spleen of the chicken and rat. (C) 1995 Wiley-Liss, Inc.