人IDE基因启动子生物信息学分析

对人IDE基因启动子进行生物信息学分析以获得人IDE基因启动子、CpG岛及转录因子结合位点特征.从UCSC基因组数据库成功获得人IDE基因5’调控区2 000 bp序列.Promoter 2.0、FPROM、NNPP预测人IDE基因分别有3个、2个、6个启动子.Relative profile score threshold选择80%、85%、90%、95%、100%时,JASPAR预测该序列存在5170、1771、454、87和5个可能的转录因子结合位点.Relative profile score threshold选择80%,搜索到6个潜在的TCF7L2转录因子结合位点.采用进化足迹法,LAGAN预测方法获得位于人和小鼠同源IDE基因启动子保守区域相同位置的转录因子结合位点为14个,包含转录因子SPI-1、cap、c-FOS、FREAC-3、c-ETS、Cdxa、HSF2等.发现一个CpG岛,位于1 303～1 705 bp 之间,大小为403 bp.人IDE基因启动子、CpG岛及转录因子结合位点的生物学信息学分析,为下一步基因表达调控实验奠定了基础.     

Raf functions downstream of Ras1 in the Sevenless signal transduction pathway.

Specification of the R7 cell fate in the developing Drosophila eye requires activation of the Sevenless (Sev) receptor tyrosine kinase, located on the surface of the R7 precursor cell, by its interaction with the Boss protein, expressed on the surface of the neighbouring R8 cell. Four genes that participate in the intracellular transmission of this signal have so far been identified and molecularly characterized: Ras1, Sos, Gap1 and sina (refs 4-8). The Drosophila homologue of the mammalian Raf-1 serine/threonine kinase, which has been implicated in signal transduction pathways activated by many receptor tyrosine kinases (reviewed in refs 9 and 10), is encoded by the raf locus (also known as l(1)polehole, Draf-1 or Draf). Here we show that the Drosophila Raf serine/threonine kinase also plays a crucial role in the R7 pathway: the response to Sev activity is dependent on raf function, and a constitutively activated Raf protein can induce R7 cell development in the absence of sev function. We also present genetic evidence suggesting that Raf acts downstream of Ras1 and upstream of Sina in this signal transduction cascade.     

A point mutation in the neu oncogene mimics ligand induction of receptor aggregation

The rat neu gene, which encodes a protein closely related to the epidermal growth factor receptor, is a proto-oncogene that can be converted into an oncogene by a point mutation. Both genes encode proteins with a relative molecular mass of 185,000 but the question of why the neu gene product, p185neu, is oncogenic, whereas the product of c-neu, p185c-neu, is not, remains unanswered. The proteins have several features common to the family of tyrosine kinase growth-factor receptors, including cysteine-rich external domains, a hydrophobic transmembrane region and a cytoplasmic tyrosine kinase domain. The oncogenic p185neu differs from p185c-neu by an amino-acid substitution in the transmembrane region of the glycoprotein: this replacement of valine by glutamic acid at position 664 induces increased intrinsic tyrosine kinase activity which is associated with transformation. Many glycoproteins with charged amino acids in the transmembrane region exist as multimeric complexes at the plasma membrane. We have therefore investigated the association state of both products of the neu gene and show that the oncoprotein p185neu is organized at the plasma membrane primarily in an aggregated form, but that p185c-neu is not. Induction of an aggregated state may mimic aspects of ligand-induced receptor aggregation resulting in enzymatic activation that leads to cellular transformation.     

Role of ion flux in the control of c-fos expression

There has been much interest in the biochemical and biophysical processes that couple extracellular signals to alterations in gene expression. While many early events associated with the treatment of cells with growth factors have been described (for example, ion flux and protein phosphorylation), it has proved difficult to establish biochemical links to gene expression. Recently, the study of such genomic control signals has been facilitated by the demonstration that the c-fos proto-oncogene is rapidly and transiently induced by treatment of several cell types with polypeptide growth factors and other growth modulating substances. In one particular system it has been shown that nerve growth factor (NGF) causes a transient induction of c-fos in the phaeochromocytoma cell line PC12, within 15 min. Furthermore, the magnitude of this induction can be modulated with pharmacological agents such as peripheral-type benzodiazepines (BZDs). Thus, the study of c-fos expression in PC12 cells could yield valuable clues to the coupling mechanisms linking cell surface activation to genomic events. Here we demonstrate that c-fos is induced in PC12 cells either by receptor-ligand interaction or by agents or conditions that effect voltage-dependent calcium channels.     

即刻早基因ZENK的基因功能及其应用进展

即刻早基因ZENK是核基因组内编码转录因子的单拷贝基因,它受多种胞外信号,如血清、生长因子、细胞因子和激素的作用在不同类型细胞内迅速、大量表达.ZENK蛋白通过C2H2型锌指识别靶基因启动子中的GC丰富序列并发生作用,从而调控靶基因的转录.ZENK基因参与细胞生长、分化、发育的调控,而且其在大脑的诱导表达与动物的学习、记忆密切关联.另有研究显示,ZENK具有很高的进化保守性,可以作为新的分子标记运用于分子系统学研究.     

Mutations of the BRAF gene in human cancer

Cancers arise owing to the accumulation of mutations in critical genes that alter normal programmes of cell proliferation, differentiation and death. As the first stage of a systematic genome-wide screen for these genes, we have prioritized for analysis signalling pathways in which at least one gene is mutated in human cancer. The RAS RAF MEK ERK MAP kinase pathway mediates cellular responses to growth signals. RAS is mutated to an oncogenic form in about 15% of human cancer. The three RAF genes code for cytoplasmic serine/threonine kinases that are regulated by binding RAS. Here we report BRAF somatic missense mutations in 66% of malignant melanomas and at lower frequency in a wide range of human cancers. All mutations are within the kinase domain, with a single substitution (V599E) accounting for 80%. Mutated BRAF proteins have elevated kinase activity and are transforming in NIH3T3 cells. Furthermore, RAS function is not required for the growth of cancer cell lines with the V599E mutation. As BRAF is a serine/threonine kinase that is commonly activated by somatic point mutation in human cancer, it may provide new therapeutic opportunities in malignant melanoma.