The regulation of gene expression by Vitamin B6.

众所周知，维生素B6的生理活性形式，5‘-磷酸吡哆醛(PLP)，是从非活性的饮食前体中提取出来的，在氨基酸代谢的许多酶反应中起辅助作用。在本研究中，我们提供了证据，表明PLP通过一种涉及转录选择因子失活的新机制来调节大鼠肝脏中的基因表达。结果：1.维生素B6缺乏大鼠肝脏中天冬氨酸氨基转移酶、白蛋白等多种基因的表达水平均高于正常对照组。由于维生素B6缺乏时这些基因的转录活性增强，因此维生素B6缺乏大鼠肝脏中各mRNAs的浓度升高可能与其转录速率增加有关。肝细胞核提取物与天冬氨酸转氨酶基因顺式元件糖皮质激素受体结合部位和…凝胶迁移率改变法检测白蛋白基因顺式元件较多。维生素B6缺乏大鼠肝脏提取液的活性明显高于对照组。由于蛋白质印迹分析估计对照组和维生素B6缺乏大鼠肝细胞核提取物中C/EBP的浓度基本相同，因此对照肝提取物结合活性降低可能是由于PLP和/或其类似物使转录因子失活所致。用1 mM PLP预孵育5分钟，观察转录因子的DNA结合抑制作用。考察了PLP及其类似物在体外对核提取液结合活性的影响，结果表明，只有PLP能有效地抑制这一结合。使用重组HNF1.6也得到了相同的结果。观察到其他转录因子如HNF3、HNF4和SP1的DNA结合受到抑制，对PLP识别的转录因子的结合部位以及PLP调控基因表达的生理意义的研究取得了积极进展。较少

It was generally known that the physiologically active form of the vitamin B6, pyridoxal 5'-phosphate (PLP), is derived from inactive dietary precursors and functions as a cofactor in numerous enzyme reactions of amino acid metabolism. In the present study, we provide evidence to suggest that PLP modulates gene expression in rat liver through a novel mechanism that involves inactivation of transcrioption factors.1. The level of several mRNA icluding aspartate aminotransferase mRNA and albumin mRNA in the liver of vitamin B6-deficient rats were found to be higher than that of control rats.2. Scince the transcriptional activities of these genes were increased in vitamin B6 deficiency, the higher concentration of each mRNAs in the liver of vitamin B6-deficient rats could be attributed to the enhanced rate of transcription.3. The binding activities of liver nuclear extracts to the glucocorticoid receptor-binding site which is cis-element of AST gene and HNF1- and C./EBP-binding sites which … More are cis-element of albumin gene were examined by gel mobility shift assay. The activities of the extract prepared from liver of vitamin B6-deficient rats were greater than those of controls. As the concentration of C/EBP in nuclear extracts from control and vitamin B6-deficient rats, estimated by Western-blot analysis were essentially the same, the lower binding activity of the extract from control liver is probably due to inactivation of transcrition factors by PLP and/or its analogues.4. The inhibition of DNA-binding of transcription factors were observed by pre-incubation with 1 mM PLP for 5min.5. The effect of PLP and its analogues on the binding activity of nuclear extract in vitro was examined, and resulted the only PLP effectively inhibited the binding. Same results were obtained using recombinant HNF1.6. The inhibition of DNA-binding of the other transcription factors such like HNF3, HNF4 and SP1 were observed.The incestigation as to the binding site of the transcription factors which is recognize by PLP and the physiological significance on the modulation of gene expression by PLP is actively progressed. Less