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Early B-Cell Factor, E2A, and Pax-5 Cooperate To Activate the Early B Cell-Specific mb-1 Promoter

2002; Taylor & Francis; Volume: 22; Issue: 24 Linguagem: Inglês

10.1128/mcb.22.24.8539-8551.2002

1098-5549

Mikael Sigvardsson, Dawn R. Clark, Daniel Fitzsimmons, Michelle J. Doyle, Peter Aåkerblad, Thomas Breslin, Sven Bilke, Ronggui Li, Carmen Yeamans, Gongyi Zhang, James Hagman,

Ubiquitin and proteasome pathways

Previous studies have suggested that the early-B-cell-specific mb-1(Igα) promoter is regulated by EBF and Pax-5. Here, we used in vivo footprinting assays to detect occupation of binding sites in endogenous mb-1 promoters at various stages of B-cell differentiation. In addition to EBF and Pax-5 binding sites, we detected occupancy of a consensus binding site for E2A proteins (E box) in pre-B cells. EBF and E box sites are crucial for promoter function in transfected pre-B cells, and EBF and E2A proteins synergistically activated the promoter in transfected HeLa cells. Other data suggest that EBF and E box sites are less important for promoter function at later stages of differentiation, whereas binding sites for Pax-5 (and its Ets ternary complex partners) are required for promoter function in all mb-1-expressing cells. Using DNA microarrays, we found that expression of endogenous mb-1 transcripts correlates most closely with EBF expression and negatively with Id1, an inhibitor of E2A protein function, further linking regulation of the mb-1 gene with EBF and E2A. Together, our studies demonstrate the complexity of factors regulating tissue-specific transcription and support the concept that EBF, E2A, and Pax-5 cooperate to activate target genes in early B-cell development.