A dominant transcriptional silencer located 5' to the human T-cell receptor V beta 2.2 gene segment which is activated in cell lines of thymic phenotype.

We have identified a transcriptional regulatory sequence located 5' to the human T-cell receptor V beta 2.2 promoter. The upstream part of this sequence acts as a transcriptional activator in the three cell lines, Jurkat, MOLT4 and HSB2, which all have a thymic phenotype. The downstream part of the sequence exerts a dominant silencing activity in the Jurkat and MOLT4 cell lines, but not in the immature HSB2 cell line. The silencing sequence binds nuclear factor(s). Mutations of nucleotides in a short stretch of sequence, demonstrating methylation interference, abolish both the factor binding and the silencing effect. Replacement of the silencing element by a homologous sequence found 5' to the human V beta 8.1 segment, leads to a protein binding pattern which shows some DNA- protein specific complexes identical to those observed with the V beta 2.2 sequence. Interestingly, binding of nuclear factors to the V beta 2.2 silencing sequence is also observed using thymic extracts, but not using extracts from samples enriched for CD34+ cells, PBL, EBV cell lines or the HeLa cell line.