KLFs对珠蛋白基因表达和红系分化的调控作用

Krüppel样因子(Krüppel-like factors, KLFs)是一组与真核基因转录调控密切相关的锌指蛋白.KLFs高度保守的羧基末端含3个串联的Cys2His2型锌指结构,用于结合GC盒和CACCC盒等DNA序列. 红细胞中特异表达的珠蛋白基因和许多红系调控因子中都含有CACCC盒.已有研究发现,多个KLFs通过结合CACCC盒参与调控珠蛋白基因表达和红系分化,例如,KLF1通过结合β-珠蛋白启动子和位点控制区(locus control region, LCR),促进β-珠蛋白的表达、γ-向β-珠蛋白基因的转换和红系分化;KLF2、KLF11和KLF13分别促进ε-和γ-珠蛋白基因的表达;KLF4促进α-和γ-珠蛋白基因的表达;KLF3和KLF8则抑制ε-和γ-珠蛋白基因的表达. 本文综述了KLFs调控珠蛋白基因表达和红系分化的研究进展.     

蒙古族、朝鲜族和壮族中腺苷酸激酶、腺苷脱氨酶、血清触珠蛋白、α_1-抗胰蛋白酶的多态性

调查了中国内蒙古的蒙古族、吉林的朝鲜族和广西壮族的红细胞腺苷酸激酶(AK)、腺苷脱氨酶(ADA)及血清触珠蛋白(Hp)、a_1-抗胰蛋白酶(a_1-AT)的遗传多态性。蒙古族、朝鲜族、壮族的基因频率:AK_1~1分别为0.9843、1.0000、1.0000;ADA~1分别为0.9529、0.9468、0.9573;Hp~1分别为0.2597、0.3152、0.3571;在a_1-AT中Pi~M分别为0.9953、0.9953、0.9928,Pi~s分别为0.0000、0.0000、0.0072,Pi~F分别为0.0047、0.0047、0.0000。x~2检验表明,三个民族各项指标的表型观察值都符合Hardy-Weinberg法则。     

野生型及启动子区突变的HPFHAγ基因在MEL细胞中的表达

研究了野生型Ａγ珠蛋白基因、中国型胎儿血红蛋白持续存在综合症（ＨＰＦＨ）Ａγ基因（启动子区─１９６Ｃ→Ｔ突变）及希腊型ＨＰＦＨＡγ基因（─１１７Ｇ→Ａ突变）在鼠红白血病（ＭＥＬ）ＧＭ９７９细胞中的表达。比较每个整合的Ａγ基因表达的ｍＲＮＡ量,─１９６Ｃ→Ｔ突变Ａγ基因未显示比野生型Ａγ基因明显增加的表达水平,而─１１７Ｇ→Ａ突变Ａγ基因在未分化的及ＨＭＢＡ或丁酸钠诱导分化的ＭＥＬＧＭ９７９细胞中的表达水平增加到野生型Ａγ基因相应水平的２．３倍至３．１倍。此结果提供了又一个实验证据,说明启动子─１１７Ｇ→Ａ突变是希腊型ＨＰＦＨ中胎儿Ａγ基因在成人中持续活跃表达的原因,这也为β地中海贫血和镰刀性贫血的基因治疗提供了新途径,即可以考虑用转移─１１７Ｇ→Ａ突变Ａγ基因的方法改善患者的贫血症状。     

The 5‘—flanking cis—acting elements of the human ε—globin gene associates with the nuclear matrix and binds to the nuclear matrix proteins

The nuclear matrix attachment regions(MARs) and the binding nuclear matrix proteins in the 5‘-flanking cisacting elements of the human ε-globin gene have been examined.Using in vitro DNA-matrix binding assay,it has been shown that the positive stage-specific regulatory element (ε-PREII,-446bp- -419bp) upstream of this gene could specifically associate with the nuclear matrix from K562 cells,indicating that ε-PREII may be an erythroidspecific facultative MAR.In gel mobility shift assay and Southwestern blotting assay,an erythroid-specific nuclear matrix protein (ε-NMPk) in K562 cells has been revealed to bind to this positive regulatory element (ε-PREII).Furthermore,we demonstrated that the silencer (-392bp- -177bp) upstream of the human ε-globin gene could associate with the nuclear matrices from K562,HEL and Raji cells.In addition,the nuclear matrix proteins prepared from these three cell lines could also bind to this silencer,suggesting that this silencer element might be a constitutive nuclear matrix attachment region(constitutive MAR).Our results demonstrated that the nuclear matrix and nuclear matrix proteins might play an important role in the regulation of the human ε-globin gene expression.     

Proteins binding to the 5‘—flanking regualtory elements of the human β—globin gene

The binding of nuclear proteins prepared from mouse erythroid tissue in different developmental stages to the 5‘-flanking regulatory elements of human β-globin gene,two negative control regions(NCR1,-610to-490 bp;NCR2,-338,to-233bp),was identified.Two stage specific protein factors corresponding to embryonic and fetal stages were found to be capable of binding to NCR2.These data provided evidence that the cis acting elements of the 5‘-flanking region might be involved in the developmental control of β-globin gene and NCR2 might be responsible in art for the silence of β-glolbin gene in the embryonic and fetal stages.     

用同源重组法修饰含人α类珠蛋白基因簇的细菌人工染色体

采用RecA蛋白介导的同源重组的方法,对本实验室筛选出的包含完整人α-类珠蛋白基因簇的细菌人工染色体（BAC）DNA进行删除修饰。首先采用PCR的方法,分别在预删除的HS-40增强子区域的上游和下游克隆长度约为500bp的两段同源序列,并一起克隆到构建载体pBV的XbaI和HindIII位点上,SalI酶切后回收1kb左右的片段并克隆到温度敏感的穿梭质粒pSV-RecA中,转化带有人α-类珠蛋白基因簇的BACDNA的感受态大肠杆菌DH10B,经氯霉素正筛选和镰孢菌酸的负筛选,获得发生两次同源重组后只含BACDNA而穿梭载体已丢失的菌株,经Southern杂交鉴定,获得了HS-40被定位删除的BAC突变体克隆。表明同源重组的方法可以对含有较多重复序列的BACDNA进行准确的删除修饰。 Abstract：By RecA protein mediated homologous recombination method, we successfully delet ed the HS-40 fragment from a bacterial artificial chromosome containing complete human α-globin gene cluster screened by our lab. Two mutant boxes(A and B) fra gments located at the two terminals of HS-40 were cloned into the XbaⅠ and HindIII sites of pBV building vector, then the 1.1kb A+B fragment was recove red from the building vector and inserted into the SalⅠ site of the shuttle vector pSV-RecA, competent DH10B E. Coli containing BAC DNA was tranformed by t he shuttle vector,after chloramphenicol positive selection and fusatic acid neg ative selection,two times of homologous recombination happened and the HS-40 fra gment was successfully deleted from the BAC DNA which is characterized by Southe rn blot,suggested that this method could modified BAC DNA accurately containing high percentage of repeat sequence.     

靶向敲除β-珠蛋白基因座控制区增强子HS2对K562细胞转录组的影响

人类β-地中海贫血的发病机制与β-样珠蛋白基因异常表达息息相关。人类β-样珠蛋白基因以5′-ε-Gγ-Aγ-δ-β-3′的顺序排列于β-珠蛋白基因座,受5′LCR (locus control region)中5个超敏位点(hypersensitive site,HS)5′HS5～5′HS1和3′HS1调控。其中5′HS2是最重要的增强子,能产生增强子RNA(enhancerRNA)并调控ε-globin、γ-globin和β-globin的表达。为了进一步探究K562细胞中增强子5′HS2的功能,本研究首先通过染色质构象捕获技术在人慢性髓原白血病K562细胞中探测到5′HS2介导的染色质相互作用集中在以包含CTCF(CCCTC-bindingfactor)位点的3′HS1和5′HS5为边界的拓扑结构域中,5′HS2在三维空间上与HBE1、HBG2和HBG1启动子区域相互靠近。其次运用CRISPRDNA片段编辑技术在K562细胞系中删除了增强子5′HS2。最后通过RNA-seq和CUT&Tag (cleavage under target&tagmentation)实验...     

用酵母单杂交系统筛选与人ε—珠蛋白基因表达相关的基因

人体胚胎型ε－珠蛋白基因5‘旁侧一个沉默子（－392－－177bp）对关闭该基因在胎儿期的表达起重要作用。DNaseⅠ足谠法分析已表明在沉默子区内存在着一个明显的蛋白质因子结合位点（－278－－235bp）。为了筛选与沉默子DNA特异结合的蛋白质因子,将该保护区域的DNA序列作为靶序列,采用酵母单杂交系统对人胎儿肝cDNA表达文库进行筛选,并对获得的克隆进行序列分析。初步的结果表明,已分离到了人核糖体大亚基蛋白3(ribosomal protein L3,RPL3）的全长cDNA克隆。体外凝胶电泳阻抑分析及竞争实验亦证明该蛋白质与沉默子DNA存在相互作用。提示RPL3可能通过与沉默子DNA的结合参与调节ε－珠蛋白基因的关闭。     

原红细胞在体外EPO诱导下的增殖分化特征

目的 系统了解小鼠红细胞终末分化过程中细胞增殖和分化的动力学。方法选用FVA细胞模型,利用密度梯度离心的方法从感染Friend致贫血病毒(anemia-inducing strain of Ffiend virus,FVA)的小鼠脾脏中分离出同步的原始阶段红细胞(FVA细胞)。通过研究EPO诱导下细胞的生长曲线,^3H-TdR掺入率以及细胞分化过程中β-珠蛋白(β-globin)基因的表达和血红蛋白合成的时空关系,分析FVA细胞在体外EPO诱导分化过程中增殖及分化的特性。结果 FVA细胞在EN3诱导早期生长旺盛,诱导24小时细胞数量达高峰,为0时的4倍;^3H-TdR掺入在诱导后12小时达高峰;从诱导后12小时开始有β-globin基因的转录,在24小时达高峰,随后减低;从18小时开始出现血红蛋白,至48小时,几乎全部细胞都表达大量血红蛋白。结论 本研究结果阐明了FVA细胞在体外EPO诱导下增殖及分化的动力学,为利用FVA细胞模型研究红细胞终末分化的机理提供了有用的基础信息。