猪CFTR基因特异性锌指核酸酶的筛选与鉴定

【目的】获得靶向猪囊性纤维化跨膜传导调节因子(Cystic fibrosis transmembrane conductance regulator,CFTR)基因的特异锌指核酸酶(Zinc finger nuclease,ZFN),为建立CFTR基因敲除猪细胞系提供技术支持。【方法】通过开源式(Oligomerized pool engineering,OPEN)方法筛选,首先以已知三锌指蛋白为框架,随机突变单个锌指关键位点氨基酸编码序列,建立人工三锌指蛋白随机库;然后应用细菌双杂交技术,从库中筛选出能够结合CFTR基因靶位点的三锌指蛋白;最后将获得的锌指蛋白与非限制性核酸内切酶FokⅠ组装成特异ZFN,通过酵母验证体系,检测ZFN靶向切割其识别序列的效率。【结果】获得3个人工三锌指蛋白随机库,每个库约含有2×10⁶个单克隆,通过2轮细菌双杂交筛选,分别获得48个针对CFTR基因左右两侧靶位点的三锌指蛋白。ZFN活性验证结果表明,约90%的ZFN能够在酵母细胞内实现靶向切割,获得了高效特异的ZFN。【结论】获得了猪CFTR基因高效特异的ZFN。     

一个水稻CCCH型锌指蛋白基因的表达模式分析

利用RT-PCR、生物信息学及其启动区与GUS基因的融合表达分析等方法,分析了一个水稻CCCH型锌指基因OsZF77的表达模式。OsZF77开放阅读框包含843个核苷酸,编码280个氨基酸,含有2个CCCH锌指结构域。RT-PCR分析表明该基因在水稻种子的胚乳中具有较高丰度的表达而在胚中不表达。对OsZF77上游2．5kb左右的启动子区段进行分析发现含有种子特异性表达必需的序列元件RY（CATGCATG）。进一步分析了该基因启动子区段与GUS基因融合表达载体的转基因水稻植株,结果表明GUS在种子胚乳特别是靠种皮的外围胚乳中具强表达,而在胚中检测不到GUS活性。以上结果说明该基因是一个胚乳优势表达基因。     

锌指核酸酶技术在基因治疗中的应用研究进展

锌指核酸酶技术是一种新兴的基因高效靶向修饰和调控技术,目前该技术已在人类疾病的基因治疗中得到应用,通过敲除致病基因使其丧失致病性或者通过修复突变基因使基因表达正常,实现了对多种人类疾病的基因治疗。基于提高锌指核酸酶效率、特异性和降低细胞毒性等方面的研究较少的现状,特就人工锌指核酸酶介导的基因敲除和基因同源重组修复等在人类疾病基因治疗方面的应用及存在问题进行了综述,并对相关研究的开展进行了展望。     

人工锌指蛋白文库的构建

【目的】以猪基因组为模板,扩增天然锌指,以此建立人工锌指蛋白文库,为猪基因组的定点操作及基因表达研究奠定基础。【方法】利用质粒JMB378和JMB440构建锌指文库骨架载体JMB378-ZF1-MCS,然后根据天然锌指蛋白接头序列的保守性,设计5条简并引物扩增猪基因组中的天然单锌指结构域,将其与JMB378-ZF1-MCS载体上的人工锌指ZF1中识别GGC的锌指蛋白连接,构建二锌指蛋白文库,通过酶切方式再将天然单锌指结构域插入到二锌指蛋白文库中,构建三锌指蛋白文库。测定锌指库容量及阳性率,并通过酶切和测序检测锌指库的多样性。【结果】构建了基于猪天然锌指模块的包含ZF1的三锌指蛋白文库,库容量达到1.5×106 CFU。该文库中含有一个人工锌指蛋白ZF1和2个天然型锌指蛋白,能够对基因组中所有以GGC起始的9bp靶序列进行筛选。【结论】构建了基于天然单锌指模块的三锌指蛋白文库,为构建新型锌指蛋白提供了一种可行的方法。     

水稻锌指蛋白基因CRISPR/Cas9突变体的构建及突变分析

[目的]通过CRISPR/Cas9基因编辑技术对水稻锌指蛋白基因(OsC3H54)进行基因编辑,筛选鉴定出其突变体植株,为深入研究OsC3H54的生物学功能提供良好材料,也为水稻锌指蛋白研究提供参考依据.[方法]通过E-CRISP在OsC3H54基因的外显子上设计靶点序列,将靶点序列连接至OsU6SK载体上,再与Cas9一起连接到pCAM-BIA1300双元载体上,获得CRISPR/Cas9重组双元载体,通过农杆菌介导将其转入日本晴水稻愈伤组织,利用潮霉素进行抗性筛选,获得突变体植株,并分析其靶点位置的碱基及编码氨基酸突变情况.[结果]在OsC3H54基因第2个外显子上找到2个符合靶点设计要求的靶点,分别为TG1:5'-CCGCCGCGGCTGCCTTTGGATAC-3'和TG2:5'-CCTTCCC CAATGGCGGGGGTGGC-3'.将OsU6SK载体和靶点序列正确连接的重组载体与Cas9一起连接至pCAMBIA1300双载体上,成功获得CRISPR/Cas9重组双元载体(pCAMBIA1300-Cas9-TG1和pCAMBIA1300-Cas9-TG2).通过农杆菌介导转入日本晴水稻,经潮霉素抗性筛选获得TG1靶点株系和TG2靶点株系,共16株CRISPR/Cas9突变体植株.CRISPR/Cas9突变体植株在靶点序列的突变位点位置附近出现套峰,表明2个株系的植株均发生碱基突变,其中Y1、Y2、Y3和Y4突变体植株均为单碱基插入突变,最终导致编码的氨基酸发生移码突变,蛋白翻译提前终止.[结论]水稻OsC3H54基因CRISPR/Cas9突变体植株的获得为进一步研究水稻锌指蛋白生物学功能提供了良好材料.     

中国野葡萄锌指蛋白基因的克隆及生物信息学分析

【目的】在受白粉病菌侵染的中国野葡萄叶片中克隆锌指蛋白基因全长,研究葡萄抗白粉病的分子机制。【方法】在前期采用mRNA差异显示技术获得的中国野葡萄华东葡萄株系白河35-1抗白粉病基因表达差异cDNA片段T11GG/B0324-292的基础上,利用cDNA末端快速扩增(RACE)技术克隆了该cDNA全长序列,并结合生物信息学方法对所获取的序列进行分析。【结果】该cDNA全长2663bp(GenBank登录号HM008621),具有完整的开放阅读框,基因全长2223bp,编码1个由740个氨基酸组成的锌指蛋白(Zinc finger protein),5′和3′非翻译区长度分别为395和44bp。多重比较分析表明,该基因推导的氨基酸序列与拟南芥、蒺藜苜蓿、水稻的C3H亚型CCCH型锌指蛋白的同源性分别为61%,70%和60%。【结论】利用RACE技术获得了锌指蛋白基因全长,为进一步研究锌指蛋白基因与葡萄抗白粉病的关系奠定了基础。     

Three-dimensional solution structure of a single zinc finger DNA-binding domain

The three-dimensional solution structure of a zinc finger nucleic acid binding motif has been determined by nuclear magnetic resonance (NMR) spectroscopy. Spectra of a synthetic peptide corresponding to a single zinc finger from the Xenopus protein Xfin yielded distance and dihedral angle constraints that were used to generate structures from distance geometry and restrained molecular dynamics calculations. The zinc finger is an independently folded domain with a compact globular structure in which the zinc atom is bound by two cysteine and two histidine ligands. The polypeptide backbone fold consists of a well-defined helix, starting as alpha and ending as 3(10) helix, packed against two beta strands that are arranged in a hairpin structure. A high density of basic and polar amino acid side chains on the exposed face of the helix are probably involved in DNA binding.     

Inhibition of retroviral RNA production by ZAP,a CCCH-type zinc finger protein

Cells have evolved multiple mechanisms to inhibit viral replication. To identify previously unknown antiviral activities, we screened mammalian complementary DNA (cDNA) libraries for genes that prevent infection by a genetically marked retrovirus. Virus-resistant cells were selected from pools of transduced clones, and an active antiviral cDNA was recovered. The gene encodes a CCCH-type zinc finger protein designated ZAP. Expression of the gene caused a profound and specific loss of viral messenger RNAs (mRNAs) from the cytoplasm without affecting the levels of nuclear mRNAs. The finding suggests the existence of a previously unknown machinery for the inhibition of virus replication, targeting a step in viral gene expression.     

谷子C2H2型锌指蛋白基因SiZFP182的克隆及表达分析

以‘晋谷45’和‘晋谷42’2个品种作为试验材料,采用聚乙二醇(PEG-6000)模拟干旱胁迫处理谷子幼苗,检测不同处理时间下丙二醛(MDA)的含量,评价其抗旱性。此外,在2个品种中克隆获得SiZFP182基因的cDNA全长,分析比较它们之间的序列差异;通过定量RT-PCR的方法分析SiZFP182基因在受到干旱胁迫的谷子幼苗中的表达特性。结果表明,‘晋谷45’的抗旱性强于‘晋谷42’,2个品种中SiZFP182基因的序列存在5处单碱基差异,使得编码的氨基酸序列不同。此外,PEG胁迫处理后24h内,SiZFP182基因在2个品种中的表达水平均表现出先升高后降低的趋势,处理后6~12h,该基因在‘晋谷45’中表达水平高于‘晋谷42’。初步认为‘晋谷45’的抗旱特性与‘晋谷42’对干旱敏感的特性,可能与干旱胁迫下处于幼苗期的2个品种中SiZFP182基因序列差异及表达差异相关。     

A wheat gene TaSAP17-D encoding an AN1/AN1 zinc finger protein improves salt stress tolerance in transgenic Arabidopsis

The stress-associated protein (SAP) multigene family is conserved in both animals and plants. Its function in some animals and plants are known, but it is yet to be deciphered in wheat (Triticum aestivum L.). We identified the wheat gene TaSAP17-D, a member of the SAP gene family with an AN1/AN1 conserved domain. Subcellular localization indicated that TaSAP17-D localized to the nucleus, cytoplasm, and cell membrane. Expression pattern analyses revealed that TaSAP17-D was highly expressed in seedlings and was involved in NaCl response, polyethylene glycol (PEG), cold, and exogenous abscisic acid (ABA). Constitutive expression of TaSAP17-D in transgenic Arabidopsis resulted in enhanced tolerance to salt stress, confirmed by improved multiple physiological indices and significantly upregulated marker genes related to salt stress response. Our results suggest that TaSAP17-D is a candidate gene that can be used to protect crop plants from salt stress.     

植物基因打靶的研究与应用

本文分析了影响基因打靶效率的因素,并指出提高同源重组利用率和在靶基因位点处引入DNA双键断裂可以提高基因打靶效率,总结了近年来这两方面尝试在植物中的研究进展,并与一些其他物种中的研究作出比较.     

奶牛乳腺炎抗性候选基因多态性研究进展

目的揭示牛科物种FEZF2基因的功能及其差异。方法从NCBI和Ensembl数据库下载牛科主要家畜FEZF2基因序列及用于比较的非牛科物种的同源序列,采用生物信息学和比较基因组学方法对牛科家畜FEZF2基因的结构、编码蛋白的理化特征、氨基酸组成、基序和保守结构域、高级结构、参与的生物学路径、分子功能及进化关系进行比较分析。结果牛科动物间FEZF2基因转录区的结构存在差异,表现为非翻译区和内含子的序列长度不一致,但它们的编码序列(coding sequence,CDS)结构模式一致,与非牛科动物的CDS结构具有共线性关系。牛科动物FEZF2蛋白都是在核内发挥生物学功能的亲水性蛋白,无信号肽序列及跨膜结构域,都含有1个COG5048保守的锌指结构域。预测显示：FEZF2蛋白参与的生物学过程主要与神经元发育调节有关,分子功能主要是与染色质结合、转录激活或抑制有关。牛科与非牛科哺乳动物的FEZF2序列都存在1个连续的甘氨酸序列重复区,水牛、牦牛、绵羊和山羊均为13G型,但普通牛和瘤牛存在12G和13G两个等位基因。各牛科物种FEZF2蛋白在氨基酸组成、序列一致性、理化特征、基序、结构域和高级结构上存在相似性,但在牛科的不同属间存在一定差异。系统发育分析显示：牛科同属动物的FEZF2蛋白遗传关系较近。结论本研究揭示牛科家畜间FEZF2基因CDS的结构模式高度一致;FEZF2作为核内功能蛋白可能参与了牛科物种的神经元发育和机体免疫等过程的基因表达调控。     

Binding of the Wilms' tumor locus zinc finger protein to the EGR-1 consensus sequence

The Wilms' tumor locus (WTL) at 11p13 contains a gene that encodes a zinc finger-containing protein that has characteristics of a DNA-binding protein. However, binding of this protein to DNA in a sequence-specific manner has not been demonstrated. A synthetic gene was constructed that contained the zinc finger region, and the protein was expressed in Escherichia coli. The recombinant protein was used to identify a specific DNA binding site from a pool of degenerate oligonucleotides. The binding sites obtained were similar to the sequence recognized by the early growth response-1 (EGR-1) gene product, a zinc finger-containing protein that is induced by mitogenic stimuli. A mutation in the zinc finger region of the protein originally identified in a Wilms' tumor patient abolished its DNA-binding activity. These results suggest that the WTL protein may act at the DNA binding site of a growth factor-inducible gene and that loss of DNA-binding activity contributes to the tumorigenic process.