NF-κB and Oct-2 Synergize to Activate the Human 3′ Igh hs4 Enhancer in B Cells

Abstract

In B cells, the Igh gene locus contains several DNase I-hypersensitive (hs) sites with enhancer activity. These include the 3′ Igh enhancers, which are located downstream of the Cα gene(s) in both mouse and human. In vivo experiments have implicated murine 3′ enhancers, hs3B and/or hs4, in class switching and somatic hypermutation. We previously reported that murine hs4 was regulated by NF-κB, octamer binding proteins, and Pax5 (B cell-specific activator protein). In this study we report that human hs4 is regulated differently. EMSAs and Western analysis of normal B cells before and after stimulation with anti-IgM plus anti-CD40 showed the same complex binding pattern formed by NF-κB, Oct-1, and Oct-2 (but not by Pax5). A similar EMSA pattern was detected in mature human B cell lines (BL-2, Ramos, and HS-Sultan) and in diffuse large B cell lymphoma cell lines, although yin yang 1 protein (YY1) binding was also observed. We have confirmed the in vivo association of these transcription factors with hs4 in B cells by chromatin immunoprecipitation assays. The diffuse large B cell lymphoma cell lines had a distinctive slow-migrating complex containing YY1 associated with Rel-B. We have confirmed by endogenous coimmunoprecipitation an association of YY1 with Rel-B, but not with other NF-κΒ family members. Transient transfection assays showed robust hs4 enhancer activity in the mature B cell lines, which was dependent on synergistic interactions between NF-κB and octamer binding proteins. In addition, human hs4 enhancer activity required Oct-2 and correlated with expression of Oct coactivator from B cells (OCA-B).

Chemotherapeutic drugs sensitize cancer cells to TRAIL-mediated apoptosis: up-regulation of DR5 and inhibition of Yin Yang 1

“…Our findings show that YY1 negatively regulates DR5 transcription. YY1 has been shown to regulate the transcriptional activity of a series of gene promoters, acting either as activator or repressor (16,41,42). Negative regulation of death receptors by YY1 has been reported for Fas (19), whereas a putative YY1-binding site, with still unknown function, has also been identified in the mouse p75 TNF receptor promoter (43).…”

Oct transcription factors mediate t(14;18) lymphoma cell survival by directly regulating bcl-2 expression

“…The increased expression of Oct-2 in t(14;18) lymphoma cells and its ability to interact with the P2 promoter region may explain the activation of the bcl-2 P2 promoter in this cell type. However, it is likely that Oct-2 is able to interact with other sequences affecting bcl-2 expression in t(14;18) lymphoma cells, especially those of the Ig enhancer (Sepulveda et al, 2004). Nonetheless, increased expression of Oct-2 and Bcl-2 is observed in other malignancies that lack this translocation, and it is probable that Oct-2 affects bcl-2 expression in those cell types as well by directly interacting with the bcl-2 promoter.…”

The NF-κB Canonical Pathway Is Involved in the Control of the Exonucleolytic Processing of Coding Ends during V(D)J Recombination

“…However, selection partially corrected the defect in exonucleolytic processing, resulting in a lesser abnormality in the productive repertoire. It is well-established that NF-B regulates different aspects of B cell apoptosis (2,9,12), proliferation (10,11,48), maturation (6, 9, 13, 49 -51), survival (8,49,52), class switch and Ig gene recombination (11,14,23,35,(53)(54)(55)(56)(57). In vitro studies examining Ikk␥ Ϫ/Ϫ embryonic stem cells cocultured with bone marrow cells (52) and in vivo studies using Mb-1Cre-transgenic mice lacking Ikk␥ from the B cell progenitor stage on (48) Previous studies have shown that NF-B signaling is defective in B cells of HED-ID patients (50).…”