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Franco Acevedo A, Mack JJ, Valenzuela NM. The transcriptional repressor BCL6 regulates CXCR3 chemokine and HLA II expression in endothelial cells. Am J Transplant 2024:S1600-6135(24)00449-0. [PMID: 39074669 DOI: 10.1016/j.ajt.2024.07.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 07/08/2024] [Accepted: 07/23/2024] [Indexed: 07/31/2024]
Abstract
IFNγ induces an endothelial pro-immunogenic phenotype through the JAK/STAT1 pathway, which can shape the activation of alloreactive leukocytes in transplant rejection. In immune cells, the DNA binding protein BCL6 controls transcription of inflammatory genes. This study tested if BCL6 modulates IFNγ-induced gene expression in endothelial cells (EC). In vitro, BCL6 was IFNγ-inducible in primary human endothelium, along with CXCR3 chemokines and HLA. BCL6 was also increased in human cardiac transplants during acute rejection, as were HLA II and CXCL9. Knockdown of BCL6 augmented, while overexpression and BTB domain inhibitors (BCL6-BTBi) suppressed, HLA II and CXCR3 chemokine expression but not HLA I. Further, BCL6 had a greater effect on HLA-DR and DP, but was less involved in regulating HLA-DQ expression. The effect correlated with BCL6 binding motifs in or near affected genes. The BCL6 DNA recognition sequence was highly similar to that of STAT1, and BTBi reduced STAT1's transcriptional activity in vitro. Our results show for the first time that BCL6 selectively controls IFNγ-induced endothelial gene expression, advancing our understanding of the endogenous mechanisms regulating donor immunogenicity.
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Affiliation(s)
- Adriana Franco Acevedo
- Department of Pathology and Laboratory Medicine, University of California, Los Angeles, USA
| | - Julia J Mack
- Department of Cardiology, University of California, Los Angeles, USA
| | - Nicole M Valenzuela
- Department of Pathology and Laboratory Medicine, University of California, Los Angeles, USA.
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Ke X, Zhang R, Yao Q, Duan S, Hong W, Cao M, Zhou Q, Zhong X, Zhao H. Alternative splicing of medaka bcl6aa and its repression by Prdm1a and Prdm1b. FISH PHYSIOLOGY AND BIOCHEMISTRY 2021; 47:1229-1242. [PMID: 34218391 DOI: 10.1007/s10695-021-00980-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 06/24/2021] [Indexed: 06/13/2023]
Abstract
Bcl6 and Prdm1 (Blimp1) are a pair of transcriptional factors that repressing each other in mammals. Prdm1 represses the expression of bcl6 by binding a cis-element of the bcl6 gene in mammals. The homologs of Bcl6 and Prdm1 have been identified in teleost fish. However, whether these two factors regulate each other in the same way in fish like that in mammals is not clear. In this study, the regulation of bcl6aa by Prdm1 was investigated in medaka. The mRNA of bcl6aa has three variants (bcl6aaX1-X3) at the 5'-end by alternative splicing detected by RT-PCR. The three variants can be detected in adult tissues and developing embryos of medaka. Prdm1a and prdm1b are expressed in the tissues and embryos where and when bcl6aa is expressed. The expression of prdm1a was high while the expression of bcl6aa was low, and vice versa, detected in the spleen after stimulation with LPS or polyI:C. In vitro reporter assay indicated that bcl6aa could be directly repressed by both Prdm1a and Prdm1b in a dosage-dependent manner. After mutation of the key base, G, of all predicted binding sites in the core promoter region of bcl6aa, the repression by Prdm1a and/or Prdm1b disappeared. The binding site of Prdm1 in the bcl6aa gene is GAAAA(T/G). These results indicate that both Prdm1a and Prdm1b directly repress the expression of bcl6aa by binding their binding sites where the 5'-G is critical in medaka fish.
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Affiliation(s)
- Xiaomei Ke
- Hubei Key Laboratory of Gene Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, Hubei, China
| | - Runshuai Zhang
- Hubei Key Laboratory of Gene Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, Hubei, China
| | - Qiting Yao
- Hubei Key Laboratory of Gene Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, Hubei, China
| | - Shi Duan
- Hubei Key Laboratory of Gene Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, Hubei, China
| | - Wentao Hong
- Hubei Key Laboratory of Gene Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, Hubei, China
| | - Mengxi Cao
- Hubei Key Laboratory of Environmental and Health Effects of Persistent Toxic Substances, Institute of Environment and Health, Jianghan University, Wuhan, 430056, China
| | - Qingchun Zhou
- Hubei Key Laboratory of Gene Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, Hubei, China
| | - Xueping Zhong
- Hubei Key Laboratory of Gene Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, Hubei, China
| | - Haobin Zhao
- Hubei Key Laboratory of Gene Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, Hubei, China.
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Expression of the alternative splicing variants of bcl6b in medaka Oryzias latipes. Comp Biochem Physiol B Biochem Mol Biol 2018; 227:83-89. [PMID: 30292753 DOI: 10.1016/j.cbpb.2018.10.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 10/01/2018] [Indexed: 01/01/2023]
Abstract
Bcl6B, also known as BAZF, plays important roles in the immune response, repression of cancers, and maintenance of spermatogonial stem cells in mammals. In this study, the homologous gene bcl6b and its 5 alternative splicing variants, namely bcl6bX1 to bcl6bX5, were isolated from medaka fish, Oryzias latipes. Medaka bcl6b possesses conserved domains such as BTB domain, RD2 domain and four zinc fingers. Medaka bcl6bX1 to bcl6bX3 possess all three previously mentioned domains with minor differences in sequences. Medaka bcl6bX4 possesses only the BTB domain due to premature stopping, and bcl6bX5 possesses both the BTB domain and zinc fingers without the RD2 domain. Medaka bcl6b was expressed in the tissues including the brain, heart, gill, muscle, spleen, kidney, intestine, ovary and testes of adult fish. Medaka bcl6b was expressed in the embryos from very early stage, and could be detected clearly in the developing eyes by RT-PCR and in situ hybridization. Medaka bcl6b could respond to the stimuli of polyI:C and LPS in the kidney and spleen. Medaka bcl6bX1 to bcl6bX3 were the majority of the variants expressed in the adult tissues and the embryos, and were the major response to the stimulation of polyI:C and LPS in the spleen. These results suggested that bcl6b, including its isoforms, could function in various tissues and embryogenesis. Moreover, bcl6b might be a factor for immune response in medaka.
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Fu X, Hao Y, Mao Y, Qian Y, Qian Z, Li T, He D, Xiao X. Absence of the first two zinc fingers in BCL6 causes the loss of inhibitory effects on cell growth. Mol Med Rep 2015; 11:3828-33. [PMID: 25585900 DOI: 10.3892/mmr.2015.3185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 10/01/2014] [Indexed: 11/05/2022] Open
Abstract
BCL6ZF is a novel transcript of BCL6, which lacks the first two zinc fingers of BCL6. It has been established that BCL6 acts as a sequence‑specific transcriptional repressor, however, the functions of BCL6ZF remain undefined. By generating stably overexpressed BCL6 and BCL6ZF in NCI‑H1299 lung cancer cells, it was found that BCL6 suppressed the levels of cell growth associated with impaired G1 phase progression compared with those of the mock control cells. However, the effects of BCL6ZF on cell growth and the cell cycle were negligible. Further study of these results demonstrated that eight genes downstream of BCL6 were markedly downregulated by the overexpression of BCL6, whereas BCL6ZF suppressed only TGFBI, indicating that the loss of the first two zinc fingers caused the loss of the inhibitory effects on cell growth and transcriptional repression. In addition, it was determined that the BCL6ZF protein was not degraded as easily as BCL6 protein by the ubiquitin/proteasome pathway, implying that the loss of the first two zinc fingers changes the three‑dimensional structure of BCL6ZF. The results demonstrated that BCL6 and BCL6ZF had different role in H1299 cells both in vitro and in vivo. The loss of its inhibitory effects on cell growth and transcriptional repressions.
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Affiliation(s)
- Xiaoxing Fu
- Key Laboratory of Cell Proliferation and Regulation Biology, Ministry of Education, Beijing Normal University, Beijing 100875, P.R. China
| | - Ying Hao
- Key Laboratory of Cell Proliferation and Regulation Biology, Ministry of Education, Beijing Normal University, Beijing 100875, P.R. China
| | - Ying Mao
- Key Laboratory of Cell Proliferation and Regulation Biology, Ministry of Education, Beijing Normal University, Beijing 100875, P.R. China
| | - Yanlin Qian
- Key Laboratory of Cell Proliferation and Regulation Biology, Ministry of Education, Beijing Normal University, Beijing 100875, P.R. China
| | - Zunlei Qian
- Key Laboratory of Cell Proliferation and Regulation Biology, Ministry of Education, Beijing Normal University, Beijing 100875, P.R. China
| | - Ting Li
- Key Laboratory of Cell Proliferation and Regulation Biology, Ministry of Education, Beijing Normal University, Beijing 100875, P.R. China
| | - Dacheng He
- Key Laboratory of Cell Proliferation and Regulation Biology, Ministry of Education, Beijing Normal University, Beijing 100875, P.R. China
| | - Xueyuan Xiao
- Key Laboratory of Cell Proliferation and Regulation Biology, Ministry of Education, Beijing Normal University, Beijing 100875, P.R. China
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Huang X, Shen Y, Liu M, Bi C, Jiang C, Iqbal J, McKeithan TW, Chan WC, Ding SJ, Fu K. Quantitative proteomics reveals that miR-155 regulates the PI3K-AKT pathway in diffuse large B-cell lymphoma. THE AMERICAN JOURNAL OF PATHOLOGY 2012; 181:26-33. [PMID: 22609116 DOI: 10.1016/j.ajpath.2012.03.013] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 02/09/2012] [Accepted: 03/22/2012] [Indexed: 11/27/2022]
Abstract
The aberrant expression of microRNA-155 (miR-155), which has emerged as having a significant impact on the biological characteristics of lymphocytes, plays important roles in B-cell malignancies, such as diffuse large B-cell lymphoma (DLBCL). DLBCL is the most common non-Hodgkin's lymphoma in the adult population, accounting for approximately 40% of newly diagnosed non-Hodgkin's lymphoma cases globally. To determine the specific function of miR-155, a quantitative proteomics approach was applied to examine the inhibitory effects of miR-155 on protein synthesis in DLBCL cells. PIK3R1 (p85α), a negative regulator of the phosphatidylinositol 3-kinase (PI3K)-AKT pathway, was identified as a direct target of miR-155. A luciferase reporter was repressed through the direct interaction of miR-155 and the p85α 3'-untranslated region, and overexpression of miR-155 down-regulated both the transcription and translation of p85α. The PI3K-AKT signaling pathway was highly activated by the sustained overexpression of miR-155 in DHL16 cells, whereas knockdown of miR-155 in OCI-Ly3 cells diminished AKT activity. Taken together, our results reveal a novel target involved in miR-155 biological characteristics and provide a molecular link between the overexpression of miR-155 and the activation of PI3K-AKT in DLBCL.
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Affiliation(s)
- Xin Huang
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE 68198-3135, USA
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