Differential expression of the T cell receptor/CD3 genes and their lymphoid-specific transcription factor genes in murine T cell x fibroblast and T cell x B cell hybrids.

We generated cell hybrids between mouse T cell lymphoma EL4 cells and mouse fibroblast B82 cells (BELIII and BELIV) to examine the expression of T cell receptor (TcR)/CD3 genes and their lymphoid-specific transcription factor genes, which are normally detected in EL4 cells. In BELIII and BELIV, expression of the TcR alpha, TcR beta and CD3 delta genes was extinguished, whereas expression of the CD3 epsilon gene was still detected. Expression of the (lymphoid enhancer binding factor 1) LEF-1 gene was extinguished and that of the GATA-3 gene was hardly detected in BELIII and BELIV. Ets-1 gene expression, observed not only in EL4 cells but also in B82 cells, was considerably reduced in BELIII and BELIV. A much higher level of PEBP2 alpha A gene expression was observed in B82 cells than in EL4 cells and was preserved in BELIII and BELIV. To examine whether reduced expression of these genes is also found in T cell x B cell hybrids, we generated an additional cell hybrid between EL4 cells and mouse plasmacytoma S194 cells (SELIII). Marked differences were observed in the expression of the TcR alpha, CD3 delta, LEF-1 and PEBP2 alpha A genes in BEL and SEL hybrids. Expression of the TcR alpha, CD3 delta and LEF-1 genes, which was extinguished in BELIII and BELIV, was detected in SELIII. PEBP2 alpha A gene expression, not detected in S194 cells, was considerably reduced in SELIII. Almost the sum of the chromosomes from the parental cells were retained by, and the presence of every gene was proven, in each cell hybrid. These results suggest that suppression of the expression of lymphoid-specific transcription factor genes may precede that of the TcR/CD3 genes in the cell hybrids, and that the presence of a different trans-acting negative regulatory mechanism(s) suppresses the expression of T cell specific genes in fibroblasts and B cells.