Nuclear Factor-κB2 Represses Sp1-Mediated Transcription at the CD99 Promoter

Abstract

Downregulation of the CD99 antigen on the surface of Hodgkin's lymphoma (HL) cells via EBV LMP1-mediated NF-κB suppression of Sp1 transcriptional activity is known to be associated with the appearance of pathogenic ReedSternberg cells. Here, we show that in addition, EBV LMP1 heterologous NF-κB activators such as CD30 and CD40 repress the CD99 promoter, which contains multiple Sp1-binding sites but no NF-κB binding sites. In addition, NF-κB-inducing kinase (NIK) repressed the CD99 promoter while NIK kinase mutants and JNK inhibitory protein failed to do so. Of the NF-κB subunits, NF-κB2 (p52) alone or in combination with other Rel subunits consistently inhibited the CD99, while NF-κB1 (p50) showed a marginal repressive effect. Furthermore, while transfection of LMP1 repressed the CD99 promoter in wild-type or NF-κB1 deficient MEFs, the same repression was not observed in NF-κB2 (p52)-deficient MEFs, indicating that NF-κB2 (p52) is required for LMP1-mediated repression of the CD99 promoter. Consistently, basal activity of the CD99 promoter was significantly higher in IKKα -/-and IKKβ -/-MEFs, but not in IKKγ -/-MEFs compared to the wild-type control MEFs. Sp1-binding sites were directly used in the repression, because a synthetic Sp1 reporter with 10 Sp1-binding sites from the CD99 promoter was repressed by LMP1 or p52 transfection. These data indicate that LMP1-mediated NF-κB2 exhibits the major inhibitory role in the transcription at the CD99 promoter.

NFκB2 p52 stabilizes rhogdiβ mRNA by inhibiting AUF1 protein degradation via a miR‐145/Sp1/USP8‐dependent axis

“…NFκB p52 has been reported to repress Sp1‐mediated CD99 transcription, but to our knowledge, the mechanism by which p52 regulates Sp1 has not been explored. To this end, we examined sp1 mRNA expression in p52+/+ vs p52−/− cells and in p52−/− (vector) vs p52−/− (p52) or p52−/− (p100) cells.…”

“…NFκB p52 has been reported to repress Sp1-mediated CD99 transcription, 39 but to our knowledge, the mechanism by which p52 regulates Sp1 has not been explored. To this end, we examined sp1 FIGURE 3 NFκB2 p52 can promote RhoGDIβ protein expression and invasion abilities in T24 cells.…”

CD99 at the crossroads of physiology and pathology

“…The loss of CD99 expression is a significant molecular event for the induction of morphological and immunological phenotypes associated with Hodgkin’s and Reed-Sternberg cells (HRSCs) (Jian et al 2015 ; Kim et al 1998 , 2000 ). These cells are more resistant to attack by cytotoxic T lymphocytes (CTLs) and apoptosis, indicating that the persistent lack of CD99 surface expression in HRSCs may favor their survival (Lee et al 2011 ). In contrast, CD99 upregulation induces differentiation of Hodgkin lymphoma cells into terminal B-cells (Jian et al 2015 ).…”

CD99-Dependent Expansion of Myeloid-Derived Suppressor Cells and Attenuation of Graft-Versus-Host Disease

“…In mature T cells, CD99 delivers effective co-stimulatory signals (Oh et al, 2007). In B cells, the downregulation of CD99 by EBV-encoded latent membrane protein-1 (LMP-1) leads to the generation of Hodgkin and Reed-Sternberg cells related to Hodgkin's disease 2000;Lee et al, 2011). Moreover, transendothelial migration of monocytes is also regulated by human CD99 (Schenkel et al, 2002).…”