The regulation of gene expression by Vitamin B6.

众所周知，维生素B6的生理活性形式吡哆醛5'-磷酸（PLP）来源于无活性的膳食前体，并在氨基酸代谢的许多酶反应中发挥辅助因子的作用。在本研究中，我们提供的证据表明，PLP通过一种涉及转录因子失活的新机制调节大鼠肝脏中的基因表达。维生素b6缺乏症大鼠肝脏中天冬氨酸转氨酶mRNA和白蛋白mRNA等多种mRNA水平均高于对照组。由于这些基因的转录活性在维生素B6缺乏的情况下增加，维生素B6缺乏的大鼠肝脏中每种mrna的浓度较高可能归因于转录率的提高。采用凝胶迁移位移法检测肝核提取物与糖皮质激素受体结合位点（AST基因顺式元件）和与白蛋白基因顺式元件（HNF1-和c / ebp）结合位点的结合活性。维生素b6缺乏大鼠肝脏提取物活性明显高于对照组。由于对照和维生素b6缺乏大鼠的核提取物中C/EBP的浓度通过Western-blot分析基本相同，因此对照肝提取物的结合活性较低可能是由于PLP和/或其类似物使转录因子失活所致。1 mM PLP预孵育5min，观察对转录因子dna结合的抑制作用。研究了PLP及其类似物对体外核提取物结合活性的影响，发现只有PLP能有效抑制核提取物的结合。重组HNF1.6得到同样的结果。观察到其他转录因子如HNF3、HNF4和SP1的dna结合受到抑制。PLP识别的转录因子结合位点及其调控基因表达的生理意义的研究正在积极进行。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