目的构建6种人DNA甲基转移酶(DNMT)3B典型的异构体的真核表达载体并对其进行过表达,初步探讨其在人胚肾细胞系293A中的生物学作用。方法以人HCT116 c DNA为模板,采用高保真PCR获得DNMT3B1和DNMT3B2的全长,并以DNMT3B2为模板,利用特异的引物扩增出DNMT3B3、DNMT3B4、DNMT3B5和DNMT3B7,将PCR产物连接到真核表达载体p CMV-2B上,并对上述载体进行Bam HⅠ、EcoRⅠ双酶切和测序鉴定,鉴定正确后,将重组质粒转染293A细胞并利用G418筛选出稳定表达的克隆株,MTT法检测细胞增殖活力。结果双酶切和测序结果表明克隆了6种人DNMT3B异构体CDS序列,经蛋白印迹检测,DNMT3B异构体在293A细胞中获得稳定表达;稳定过表达DNMT3B3、DNMT3B4和DNMT3B7可以抑制细胞增殖。结论构建了人DNMT3B异构体真核表达载体及获得了其稳定表达细胞株,DNMT3B异构体蛋白对胚肾细胞系293A的增殖有不同的作用。
Hypoxic preconditioning refers to the exposure of organisms, systems, organs, tissues or cells to moderate hypoxia/ischemia that results in increased resistance to a subsequent episode of severe hypoxia/ischemia. In this article, we review recent research based on a mouse model of repeated exposure to autohypoxia. Pre-exposure markedly increases the tolerance to or protection against hypoxic insult, and preserves the cellular structure of the brain. Furthermore, the hippocampal activity amplitude and frequency of electroencephalogram, latency of cortical somatosensory-evoked potential and spinal somatosensory-evoked potential progressively decrease, while spatial learning and memory improve. In the brain, detrimental neurochemicals such as free radicals are down-regulated, while beneficial ones such as adenosine are up-regulated. Also, antihypoxia factor（s） and gene（s） are activated. We propose that the tolerance and protective effects depend on energy conservation and plasticity triggered by exposure to hypoxia via oxygen-sensing transduction pathways and hypoxia-inducible factor-initiated cascades. A potential path for further research is the development of devices and pharma-ceuticals acting on antihypoxia factor（s） and gene（s） for the prevention and treatment of hypoxia and related syndromes.
