Different tumor-derived p53 mutants exhibit distinct biological activities

In its wild-type form, the protein p53 can interfere with neoplastic processes. Tumor-derived cells often express mutant p53. Full-length mutant forms of p53 isolated so far from transformed mouse cells exhibit three common properties in vitro: loss of transformation-suppressing activity, gain of pronounced transforming potential, and ability to bind the heat shock protein cognate hsc70. A tumor-derived mouse p53 variant is now described, whose site of mutation corresponds to a hot spot for p53 in human tumors. While absolutely nonsuppressing, it is only weakly transforming and exhibits no detectable hsc70 binding. The data suggest that the ability of a p53 mutant to bind endogenous p53 is not the sole determinant of its oncogenic potential. The data also support the existence of gain-of-function p53 mutants.     

Expression of the pX gene of HTLV-I: general splicing mechanism in the HTLV family

Human T-cell leukemia virus type I (HTLV-I) is an etiological agent of adult T-cell leukemia. A viral gene pX encodes for p40X and it has been proposed that this protein trans-activates the viral long terminal repeat and possibly some cellular genes; this activation may be associated with T-cell transformation. The mechanism of pX gene expression and the primary structure of p40X are now reported. Two-step splicing generates the 2.1-kilobase pX mRNA; the initiator methionine for env becomes part of the pX protein. These splicing signals are conserved among all members of the HTLV family except for the acquired immune deficiency syndrome-associated viruses.     

基于开放染色质的全基因组水平转录调控元件的研究方法与进展

真核生物转录调控过程是大量的顺式调控元件与反式作用因子相互作用的结果.研究发现,这一调控过程与染色质核小体的动态定位相关,调控因子的结合需要裸露的无核小体的DNA区域,即开放的染色质位点.因此,高效精确地定位基因组上的开放染色质位点为成功地发掘基因组调控元件,乃至揭示基因表达调控机制提供了重要线索和有效手段.本文对开放染色质位点的定义、主要研究方法以及功能注释进行概述,希望对在基因组水平上调控元件的发掘,尤其是在植物中的应用提供借鉴.     

A regulatory SNP causes a human genetic disease by creating a new transcriptional promoter

We describe a pathogenetic mechanism underlying a variant form of the inherited blood disorder alpha thalassemia. Association studies of affected individuals from Melanesia localized the disease trait to the telomeric region of human chromosome 16, which includes the alpha-globin gene cluster, but no molecular defects were detected by conventional approaches. After resequencing and using a combination of chromatin immunoprecipitation and expression analysis on a tiled oligonucleotide array, we identified a gain-of-function regulatory single-nucleotide polymorphism (rSNP) in a nongenic region between the alpha-globin genes and their upstream regulatory elements. The rSNP creates a new promoterlike element that interferes with normal activation of all downstream alpha-like globin genes. Thus, our work illustrates a strategy for distinguishing between neutral and functionally important rSNPs, and it also identifies a pathogenetic mechanism that could potentially underlie other genetic diseases.     

A gene regulatory network subcircuit drives a dynamic pattern of gene expression

Early specification of endomesodermal territories in the sea urchin embryo depends on a moving torus of regulatory gene expression. We show how this dynamic patterning function is encoded in a gene regulatory network (GRN) subcircuit that includes the otx, wnt8, and blimp1 genes, the cis-regulatory control systems of which have all been experimentally defined. A cis-regulatory reconstruction experiment revealed that blimp1 autorepression accounts for progressive extinction of expression in the center of the torus, whereas its outward expansion follows reception of the Wnt8 ligand by adjacent cells. GRN circuitry thus controls not only static spatial assignment in development but also dynamic regulatory patterning.     

核桃JrJAZ基因家族鉴定与转录表达分析

为了揭示核桃JAZ基因家族在核桃生长发育中的作用,本研究通过构建隐马尔科夫模型与转录组数据结合的方法,在核桃全基因组数据库搜索JAZ家族基因,对该家族进行理化性质、基因结构、保守基序、启动子元件、蛋白互作预测等生物信息学和低温胁迫下的转录表达分析。结果表明,核桃JAZ基因家族包含17个成员,蛋白长度范围为138～385个氨基酸,开放阅读框为417～1 149 bp,等电点为8.47～10,全部为碱性不稳定亲水蛋白;含有典型的TIFY和jas 2个高度保守的结构域,聚类分析发现,该类基因可分为Group A、Group B、GroupC和GroupD4个亚族。在低温胁迫48h后经转录表达分析,JrJAZ1、JrJAZ3、JrJAZ4、JrJAZ5、JrJAZ7、JrJAZ9、JrJAZ15、JrJAZ16为差异表达基因,推测可能响应低温胁迫。本研究结果将为进一步研究该类基因的功能提供了重要线索和依据。     

鸡卵清蛋白基因调控序列的克隆与载体构建

卵清蛋白（ovalbumin）基因在鸡基因组中只有一对等位基因,却能每天合成分泌多达2 g的蛋白,占据卵白蛋白质的50%以上,是外源基因载体表达调控构件的首选。该研究从输卵管特异性启动子方面着手,通过对卵清蛋白基因启动子的筛选优化,找出启动子增强因子的位置以及组织特异性区域。将卵清蛋白基因上游-922～-2 073和-2 801～-3 100区域平均分成12个长度约为150 bp的序列,分别插入到-921～+38序列的上游,成功构建12个系列表达载体,为进一步筛选短缩版优化启动子提供材料;卵清蛋白基因第一内含子区域截断成300 bp左右的迷你内含子序列,成功构建8个迷你内含子系列载体,为筛选优化的迷你内含子提供必要的材料;成功分离鸡输卵管上皮细胞并优化电转染条件,通过荧光素酶活性检测初步筛选出具有最强活性重组质粒pGL4 UP 1412和内含子重组质粒pGL4 mini intron 3,同时推断出若干包含增强子序列区域。     

拟南芥叶绿体分裂突变体x17-3和pd50的基因鉴定与分析

目的叶绿体起源于内共生的蓝细菌,它通过与细菌类似的分裂方式进行增殖以维持遗传稳定。叶绿体分裂需要起源于原核和真核细胞的蛋白高度协调。拟南芥是研究叶绿体分裂的模式植物。在过去的20年中,人们对拟南芥叶绿体分裂蛋白复合体进行了初步的研究。然而, CRL基因在叶绿体分裂中的功能还不清楚。方法本研究通过突变体筛选和图位克隆鉴定得到2个新的crl突变体,分别为x17-3和pd50。通过显微观察和分子生物学方法分析了x17-3和pd50中叶绿体分裂表型、CRL基因剪接方式和mRNA含量以及叶绿素含量。最后通过转化互补和RNA干扰(RNAi)技术进一步确认了基因功能。结果x17-3和pd50的叶绿体形态与野生型相比有较大差异,表现为叶绿体体积增大,细胞中叶绿体数量减少。x17-3叶绿体数量为野生型的40%,而pd50叶绿体减少到只有1~4个,植物生长也受到明显抑制。通过粗定位及测序分析发现x17-3和pd50的CRL基因存在突变,突变位点在内含子并且影响mRNA剪接,最终导致阅读框移码突变。通过实时荧光定量PCR分析发现,pd50中CRL mRNA含量比野生型和x17-3明显降低。遗传互补实验进一步验证了x17-3和pd50中叶绿体分裂和植物生长抑制表型是CRL基因突变导致的。应用RNAi技术抑制CRL基因表达也能产生明显的叶绿体分裂异常表型。此外,pd50和x17-3的叶绿素含量比野生型明显降低。结论本项工作为进一步揭示CRL基因的功能提供新的研究材料和实验依据。