Cooperative binding of c-Myb and Pax-5 activates theRAG-2 promoter in immature B cells

Abstract

The recombination activating gene-1 (RAG-1) and RAG-2 are expressed specifically in immature lymphoid cells undergoing the recombination of antigen receptor genes. The regulation of murine RAG-2 promoter was studied and it was revealed that the ؊41/؊17 RAG-2 promoter region, which is conserved between humans and mice, was indispensable for the RAG-2 promoter activity in B IntroductionImmunoglobulin (Ig) and T-cell receptor (TCR) variable genes consist of germline variable (V), diversity (D), and joining (J) segments and are assembled during lymphocyte development by V(D)J recombination. The recombination activating gene-1 (RAG-1) and RAG-2 encode the essential and lymphocyte-specific components of V(D)J recombination machinery. Their products are sufficient for the recognition and initial cleavage of DNA containing recombination signal sequences that flank each coding segment. 1,2 During lymphocyte development, expression of RAG-1 and RAG-2 is tightly regulated. RAG genes are expressed in immature B-or T-lineage cells undergoing Ig or TCR gene rearrangements. [3][4][5][6] The failure of functional expression of RAG causes a defect in the formation of the functional antigen receptor of lymphocytes, and hence causes the block of lymphocyte development in mice and humans. [7][8][9][10] The transcription of RAG is regulated at different levels. At the chromatin level, Fuller and Storb 11 and Kitagawa et al 12 have demonstrated that alteration of chromatin structure detected by DNase I hypersensitivity was noted in the promoter region of mouse and human RAG-1 only in RAG-expressing lymphocytes, indicating that chromatin remodeling is one of the mechanisms for regulating RAG expression. At the cis-element level, Yu et al have demonstrated that about 10 kb 5Ј upstream region of RAG-2 is necessary for the expression of RAG in B-lineage cells and in CD4 Ϫ CD8 Ϫ thymocytes, and that further upstream region is required for the expression of RAG in CD4 ϩ CD8 ϩ thymocytes. 13 Monroe et al have demonstrated that about 10 kb 5Ј upstream region of RAG-2 is enough for rescuing B-and T-cell development in RAG2 Ϫ/Ϫ mice by using RAG-2 Ϫ/Ϫ blastocyst complementation. 14 These results suggest that expression of RAG is regulated by the cis-element, such as enhancer. At the promoter level, it was reported that the human RAG-1 promoter region does not confer the lymphocyte-specific expression of RAG-1. 12,[15][16][17] Regarding the promoter of RAG-2, about 300 bp 5Ј upstream region from the major transcription initiation site of mouse RAG-2 is conserved between mice and humans, [17][18][19] indicating that this region is important for the promoter activity of RAG-2. It was also demonstrated that the human RAG-2 promoter is activated not only in lymphoid cells but also in nonlymphoid cells. 17 Materials and methods Cells and cell cultureThe 18.8.1 pre-B cell line 18 and the BAL17 B cell line, 18 both of which express endogenous murine RAG-1 and RAG-2, were cultured in RPMI 1640 supplemented with 10% fetal calf serum, 100 U/mL penicill...

Role of Pax-5 Transcription Factor in Immunological Processes

“…PAX-5 также активирует экспрессию фермен-та RAG2 в процессе созревания В-лимфоцитов, действуя при этом совместно с другим транс-крипционным фактором -сMyb [24].…”

Characterization of the proximal enhancer element and transcriptional regulatory factors for murine recombination activating gene‐2

“…We also analyzed the DNase I hypersensitivity of the murine RAG-2 locus and identified three lymphoid-specific DNase I HS sites, one of which corresponded to the promoter region whereas the others corresponded to the enhancer elements [15]. At the promoter level, the mouse RAG-2 promoter, but not the human RAG-2 promoter, conferred lymphoid specificity [14,[16][17][18], and it has been shown that distinct transcriptional factors regulate lineage-specific activation of the mouse RAG-2 promoter in B and T lineage cells [19][20][21][22]. Recently, involvement of cis elements other than the RAG-2 promoter region that drive the lymphoid-and differentiation stage-specific RAG-2 expression in vivo has been reported [23][24][25], indicating the important role of the cis-acting regulatory elements, such as enhancers or silencers, in the 5 0 upstream region of mouse RAG-2.…”

Cancer Metabolic and Immune Reprogramming: The Intimate Interaction Between Cancer Cells and Microenvironment

“…E2A, Ikaros, Foxo1, Foxp1 and NF-κB were all shown to activate RAG expression by binding to Erag in murine B cells. Pax5β was reported to activate RAG2 promoter in immature B cells [73]. Chen et al [74] analyzed the protein and mRNA expressions of those transcription factors that have been found to be essential for RAG activation in B cells, including E2A (E47 and E12), Foxo1, Foxp1, Ikaros, NF-κB, and Pax5β, in four cancer cell lines.…”