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Asian Pac J Cancer Prev. 2013;14(1):359-65.

Tax is involved in up-regulation of HMGB1 expression levels by interaction with C/EBP.

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1
Clinical Laboratory Medicine Department, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.

Abstract

The high mobility group box 1 (HMGB1) protein is a multifunctional cytokine-like molecule that plays an important role in the pathogenesis of tumors. In this study, real-time polymerase chain reactions and Western blot assays indicated that HMGB1 transcriptional activity and protein level are increased in Tax+-T cells (TaxP). To clarify the mechanisms, a series of HMGB1 deletion reporter plasmids (pHLuc1 to pHLuc6) were transfected into Tax--T cells (TaxN, Jurkat) and Tax+-T cells (TaxP). We found that promoter activity in Tax+-T cells to be higher than that in Tax--T cells, indicating a significant increase in pHLuc6. Bay11-7082 (NF-κB inhibitor) treatment did not block the enhancing effect. Chromatin immunoprecipitation assays revealed that Tax was retained on a HMGB1 promoter fragment encompassing -1163 to -975. Bioinformatics analysis showed six characteristic cis-elements for CdxA, AP-1, AML-1a, USF, v-Myb, and C/EBP in the fragment in question. Mutation of cis- elements for C/EBP reduced significant HMGB1 promoter activity induced by Tax. These findings indicate that Tax enhances the expression of HMGB1 gene at the transcriptional level, possibly by interacting with C/EBP.

PMID:
23534754
DOI:
10.7314/apjcp.2013.14.1.359
[Indexed for MEDLINE]
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