Kumar Parveen, Gullberg Urban, Olsson Inge, Ajore Ram
Department of Hematology, Lund University, Lund, Sweden.
PLoS One. 2015 May 14;10(5):e0123725. doi: 10.1371/journal.pone.0123725. eCollection 2015.
The myeloid translocation gene 16 (MTG16) co-repressor down regulates expression of multiple glycolytic genes, which are targets of the hypoxia-inducible factor 1 (HIF1) heterodimer transcription factor that is composed of oxygen-regulated labile HIF1α and stable HIF1β subunits. For this reason, we investigated whether MTG16 might regulate HIF1 negatively contributing to inhibition of glycolysis and stimulation of mitochondrial respiration. A doxycycline Tet-On system was used to control levels of MTG16 in B-lymphoblastic Raji cells. Results from co-association studies revealed MTG16 to interact with HIF1α. The co-association required intact N-terminal MTG16 residues including Nervy Homology Region 1 (NHR1). Furthermore, electrophoretic mobility shift assays demonstrated an association of MTG16 with hypoxia response elements (HREs) in PFKFB3, PFKFB4 and PDK1 promoters in-vitro. Results from chromatin immunoprecipitation assays revealed co-occupancy of these and other glycolytic gene promoters by HIF1α, HIF1β and MTG16 in agreement with possible involvement of these proteins in regulation of glycolytic target genes. In addition, MTG16 interacted with prolyl hydroxylase D2 and promoted ubiquitination and proteasomal degradation of HIF1α. Our findings broaden the area of MTG co-repressor functions and reveal MTG16 to be part of a protein complex that controls the levels of HIF1α.
髓系易位基因16（MTG16）共抑制因子下调多个糖酵解基因的表达，这些基因是由氧调节的不稳定HIF1α和稳定的HIF1β亚基组成的缺氧诱导因子1（HIF1）异二聚体转录因子的靶标。因此，我们研究了MTG16是否可能负向调节HIF1，从而抑制糖酵解并刺激线粒体呼吸。采用强力霉素Tet-On系统来控制B淋巴细胞Raji细胞中MTG16的水平。共关联研究结果显示MTG16与HIF1α相互作用。这种共关联需要完整的MTG16 N端残基，包括Nervy同源区域1（NHR1）。此外，电泳迁移率变动分析表明MTG16在体外与磷酸果糖激酶-2/果糖-2,6-二磷酸酶3（PFKFB3）、磷酸果糖激酶-2/果糖-2,6-二磷酸酶4（PFKFB4）和丙酮酸脱氢酶激酶1（PDK1）启动子中的缺氧反应元件（HREs）相关联。染色质免疫沉淀分析结果显示HIF1α、HIF1β和MTG16共同占据这些以及其他糖酵解基因启动子，这与这些蛋白质可能参与糖酵解靶基因的调控一致。此外，MTG16与脯氨酰羟化酶D2相互作用，并促进HIF1α的泛素化和蛋白酶体降解。我们的研究结果拓宽了MTG共抑制因子功能的领域，并揭示MTG16是控制HIF1α水平的蛋白质复合物的一部分。
