Junjappa Raghu Patil, Kim Hyun-Kyoung, Park Seong Yeol, Bhattarai Kashi Raj, Kim Kyung-Woon, Soh Jae-Won, Kim Hyung-Ryong, Chae Han-Jung
Department of Pharmacology and New Drug Development Research Institute, Chonbuk National University Medical School, Jeonju 54896, Korea.
Animal Biotechnology Division, National Institute of Animal Science, Rural Development Administration (RDA), Wanju-gun, Chonbuk 54875, Korea.
Cancers (Basel). 2019 Jul 11;11(7):974. doi: 10.3390/cancers11070974.
Transmembrane Bax Inhibitor Motif-containing 6 (TMBIM6) is upregulated in several cancer types and involved in the metastasis. Specific downregulation of TMBIM6 results in cancer cell death. However, the TMBIM6 gene transcriptional regulation in normal and cancer cells is least studied. Here, we identified the core promoter region (-133/+30 bp) sufficient for promoter activity of TMBIM6 gene. Reporter gene expression with mutations at transcription factor binding sites, EMSA, supershift, and ChIP assays demonstrated that Sp1 is an essential transcription factor for basal promoter activity of TMBIM6. The TMBIM6 mRNA expression was increased with Sp1 levels in a concentration dependent manner. Ablation of Sp1 through siRNA or inhibition with mithramycin-A reduced the TMBIM6 mRNA expression. We also found that the protein kinase-C activation stimulates promoter activity and endogenous TMBIM6 mRNA by 2- to 2.5-fold. Additionally, overexpression of active mutants of PKCι, PKCε, and PKCδ increased TMBIM6 expression by enhancing nuclear translocation of Sp1. Immunohistochemistry analyses confirmed that the expression levels of PKCι, Sp1, and TMBIM6 were correlated with one another in samples from human breast, prostate, and liver cancer patients. Altogether, this study suggests the involvement of Sp1 in basal transcription and PKC in the enhanced expression of TMBIM6 in cancer.
含跨膜Bax抑制剂基序6（TMBIM6）在多种癌症类型中上调，并参与转移过程。TMBIM6的特异性下调会导致癌细胞死亡。然而，TMBIM6基因在正常细胞和癌细胞中的转录调控研究最少。在此，我们确定了足以驱动TMBIM6基因启动子活性的核心启动子区域（-133/+30 bp）。通过转录因子结合位点突变的报告基因表达、电泳迁移率变动分析（EMSA）、超迁移分析和染色质免疫沉淀（ChIP）分析表明，Sp1是TMBIM6基础启动子活性的关键转录因子。TMBIM6 mRNA表达随Sp1水平呈浓度依赖性增加。通过小干扰RNA（siRNA）敲除Sp1或用放线菌素A抑制可降低TMBIM6 mRNA表达。我们还发现蛋白激酶C激活可使启动子活性和内源性TMBIM6 mRNA增加2至2.5倍。此外，PKCι、PKCε和PKCδ活性突变体的过表达通过增强Sp1的核转位增加了TMBIM6的表达。免疫组织化学分析证实，在来自人类乳腺癌、前列腺癌和肝癌患者的样本中，PKCι、Sp1和TMBIM6的表达水平相互关联。总之，本研究表明Sp1参与基础转录，而PKC参与癌症中TMBIM6的表达增强。
