Purification of a novel MHC class I element binding activity from thymus nuclear extracts reveals that thymic RBP-Jkappa/CBF1 binds to NF-kappaB-like elements
Shirakata, Y.; Shuman, J.D.; Coligan, J.E.
Journal of Immunology 156(12): 4672-4679
1996
ISSN/ISBN: 0022-1767 PMID: 8648111 Document Number: 466406
We purified a DNA binding protein that recognizes a portion of the MHC class I regulatory element region 1/NF-kappa-B binding site whose expression correlates with the expression of a MHC class I transgene in the thymus. The N-terminal amino acid sequence and the molecular size matched the RBP-J-kappa protein, also known as the EBV C-promoter binding factor, CBF1. Antipeptide sera reactive with RBP-J-kappa/CBF1 also reacted with this protein in gel mobility shift assays. Although RBP-J-kappa/CBF1 is ubiquitously expressed, binding to the MHC class Ia NF-kappa-B site was limited to the thymus. Comparison of the DNA binding specificities of RBP-J-kappa/CBF1 in thymic and splenic nuclear extracts revealed strong binding from both extracts to an IFN-beta kappa-B site containing the RBP-J-kappa/CBF1 consensus sequence (CGTGGGAA). In contrast, only the thymic nuclear extract showed strong DNA binding activity with probes containing the NF-kappa-B recognition sequences present in the MHC class Ia, IL-2R-alpha, and granulocyte-macrophage CSF promoters. Thus, RBP-J-kappa/CBF1 in thymic extracts demonstrates a clearly distinguishable DNA binding specificity that correlates with tissue-specific expression of a class I transgene. This, coupled with the fact that our previous study showed enhanced expression of the transgene in CD4+CD8+ thymocytes, suggests that RBP-J-kappa/CBF1 may play a role in the development of the immune system.