p15Ink4b is a critical tumour suppressor in the absence of p16Ink4a

The CDKN2b-CDKN2a locus on chromosome 9p21 in human (chromosome 4 in mouse) is frequently lost in cancer. The locus encodes three cell cycle inhibitory proteins: p15INK4b encoded by CDKN2b, p16INK4a encoded by CDKN2a and p14ARF (p19Arf in mice) encoded by an alternative reading frame of CDKN2a (ref. 1). Whereas the tumour suppressor functions for p16INK4a and p14ARF have been firmly established, the role of p15INK4b remains ambiguous. However, many 9p21 deletions also remove CDKN2b, so we hypothesized a synergistic effect of the combined deficiency for p15INK4b, p14ARF and p16INK4a. Here we report that mice deficient for all three open reading frames (Cdkn2ab-/-) are more tumour-prone and develop a wider spectrum of tumours than Cdkn2a mutant mice, with a preponderance of skin tumours and soft tissue sarcomas (for example, mesothelioma) frequently composed of mixed cell types and often showing biphasic differentiation. Cdkn2ab-/- mouse embryonic fibroblasts (MEFs) are substantially more sensitive to oncogenic transformation than Cdkn2a mutant MEFs. Under conditions of stress, p15Ink4b protein levels are significantly elevated in MEFs deficient for p16Ink4a. Our data indicate that p15Ink4b can fulfil a critical backup function for p16Ink4a and provide an explanation for the frequent loss of the complete CDKN2b-CDKN2a locus in human tumours.     

刀额新对虾周期蛋白B基因的分子克隆及序列分析

周期蛋白B(cyclin B)是真核生物细胞周期的一种重要调控原件,通过调节周期蛋白依赖性蛋白激酶(cyclindependent kinase,CKD)的活性可以控制细胞周期.运用RACE(rapid-amplification of cDNA ends)技术克隆了刀额新对虾(Metapendeusensis)cyclin B基因.刀额新对虾cyclin B的cDNA全长为1681 bp,5′端非编码区为111 bp,3 ′端非编码区为355 bp,开放阅读框为1215 bp,编码404个氨基酸,平均分子质量为45767.9 u,pl为8.81.Blast比对后发现,其氧摹酸序列与斑节对虾(Penaeus monodon)的同源性达约90％.基于cyclin B序列所绘制的进化树基本上能反映出各物种间的进化关系.半定量RT-PCR结果显示,刀额新对虾的cyclinB基因在不同组织表达中具有明显的组织特异性,在鳃、卵巢和心脏中有较高的表达量,在眼柄神经节和胸神经节中表达量较低.推测该差异性主要与cyclin B在细胞周期中调控细胞分裂的功能有关.     

Cloning of a novel gene encoding human thioredoxin-like protein

mRNA differential display (DDRT-PCR) has been used to analyze different human fetal brain tissues of different developmental stages (13- and 33-week). According to the sequence of one EST obtained in this assay, a pair of primers have been designed to screen the arrayed human fetal brain cDNA library. A1 .2-kb cDNA clone has been found. This cDNA consists of an 867 bp open reading frame, a 132 bp 5' untranslated sequence and a 209 bp 3' untranslated sequence with a typical polyadenylation signal. The coding region predicts a protein of 289 amino acids. Its N-terminal of 105 residues is highly homologous to human thioredoxin, while no homology has been found in the databases with its C-terminal of 184 residues. Its N-terminal region also contains the conserved active site sequence CGPC (Cys-Gly-Pro-Cys) of thioredoxin. It was named human Thioredoxin-like gene (hTRXL).     

A superantigen encoded in the open reading frame of the 3' long terminal repeat of mouse mammary tumour virus.

Mice express a collection of superantigens, which bind to class II major histocompatibility proteins and interact with T cells bearing particular V beta chains as part of their alpha beta receptors. These superantigens have been suggested to be encoded by exogenous or endogenous mouse mammary tumour viruses. One such superantigen is now shown to be encoded in the open reading frame of the long terminal repeat of a mammary tumour virus, a gene of previously unknown function.     

A Tyr/Ser protein phosphatase encoded by vaccinia virus.

Protein tyrosine phosphorylation is associated with alterations in receptor activity, cellular proliferation and modulation of the cell cycle. Inappropriate tyrosine phosphorylation can lead to unrestrained cell growth and oncogenesis. Enzymes important in tyrosine dephosphorylation have also been described. Protein tyrosine phosphatases (PTPases) consist of two families. There is a receptor-like family of PTPases with an extracellular domain, transmembrane-spanning region and typically two repeated phosphatase domains. Proteins of the non-receptor-like family have a single catalytic phosphatase domain, show a substrate specificity for Tyr phosphate and will not hydrolyse Ser or Thr phosphate. Here we report that the vaccinia virus genome contains an open reading frame which shares amino-acid sequence identity with the PTPases. The purified protein encoded by the vaccinia virus H1 open reading frame expressed in bacteria hydrolyses substrates containing phosphotyrosine and phosphoserine. Mutagenesis of an essential Cys in the vaccinia phosphatase abolishes catalytic activity directed towards both substrates, suggesting that hydrolysis proceeds by a common mechanism. Understanding the function of the H1-encoded protein will help to define the role of the phosphatase in viral replication and pathogenesis.     

Cloning,sequencing and structural analysis of a pea cDNA encoding EF-1α

A cDNA library with the capacity of 2.0 × 10⁶ was constructed using mRNA extracted, from gibberellic acid (GA)-treated G2 pea seedlings and a 1.6 kb cDNA with 100 nucleotides of 5′ non-coding region and 223 nucleotides of 3′ non-coding region was obtained by random screening. The DNA fragment contains an open reading frame of 1 344 nucleotides and encodes 447 amino acids. Sequence analysis of DNA and deduced polypeptide demonstrated that it encoded for a pea elongation factor 1-alpha (EF-1α). The functional domains of EF-1α is well conserved and EF-1α can be a good candidate for studying molecular evolution.     

Complete nucleotide sequence of the AIDS virus, HTLV-III

The complete nucleotide sequence of two human T-cell leukaemia type III (HTLV-III) proviral DNAs each have four long open reading frames, the first two corresponding to the gag and pol genes. The fourth open reading frame encodes two functional polypeptides, a large precursor of the major envelope glycoprotein and a smaller protein derived from the 3'-terminus long open reading frame analogous to the long open reading frame (lor) product of HTLV-I and -II.     

筛选hALR的相互作用蛋白基因(英)

为筛选与人肝再生增强因子(hALR)相互作用蛋白的基因,探讨肝再生增强因子在肝再生过程中的分子生物学机制,将人肝再生增强因子基因的开放读码框片断,重组入载体pGBKT7构建成“诱饵”质粒pGBKT7-hALR,然后用酵母双杂交系统从预转化酵母菌Y187的成人肝细胞cDNA文库中筛选与人肝再生增强因子相互作用蛋白的基因.筛出的阳性克隆基因序列被测出后,经GenBank查询,结果发现它们分别是血清白蛋白、金属硫蛋白、硒蛋白类似物、Na+/K+ ATPase和一个未知功能的蛋白的部分序列.这初步克隆了与hALR相互作用的蛋白基因,为进一步探讨ALR在肝再生过程中的作用机制奠定了基础.     

筛选hALR的相互作用蛋白基因

为筛选与人肝再生增强因子(hALR)相互作用蛋白的基因，探讨肝再生增强因子在肝再生过程中的分子生物学机制，将人肝再生增强因子基因的开放读码框片断，重组入载体pGBKT7构建成“诱饵”质粒pGBKT7—hALR，然后用酵母双杂交系统从预转化酵母菌Y187的成人肝细胞cDNA文库中筛选与人肝再生增强因子相互作用蛋白的基因。筛出的阳性克隆基因序列被测出后，经GenBank查询，结果发现它们分别是血清白蛋白、金属硫蛋白、硒蛋白类似物、Na^ ／K^ ATPase和一个未知功能的蛋白的部分序列。这初步克隆了与hALR相互作用的蛋白基因，为进一步探讨ALR在肝再生过程中的作用机制奠定了基础。     

Glycosyl-phosphatidylinositol linkage as a mechanism for cell-surface expression of immunoglobulin D.

The B-cell antigen receptor of the IgM and IgD class is a multimeric complex consisting of the membrane-bound form of the immunoglobulin molecule and two other proteins, Ig-alpha and Ig-beta. The Ig-alpha and Ig-beta proteins form a disulphide-linked alpha/beta heterodimer and are encoded by the mb-1 (ref 9, 10) and B29 genes, respectively. Surface expression of the membrane-bound IgM molecule requires assembly with the alpha/beta heterodimer. The IgD molecule, however, can be expressed on the cell surface in an alpha/beta-dependent and -independent form. We show here that in the alpha/beta-independent form the IgD molecule is anchored in the plasma membrane through a glycosyl-phosphatidylinositol linker. In the presence of the alpha/beta heterodimer, most of the otherwise glycosyl-phosphatidylinositol-linked IgD molecule is expressed on the cell surface as transmembrane proteins.     

Homology of a yeast actin-binding protein to signal transduction proteins and myosin-I

In yeast, the cortical actin cytoskeleton seems to specify sites of growth of the cell surface. Because the actin-binding protein ABP1p is associated with the cortical cytoskeleton of Saccharomyces cerevisiae, it might be involved in the spatial organization of cell surface growth. ABP1p is localized to the cortical cytoskeleton and its overproduction causes assembly of the cortical actin cytoskeleton at inappropriate sites on the cell surface, resulting in delocalized surface growth. We have now cloned and sequenced the gene encoding ABP1p. ABP1p is a novel protein with a 50 amino-acid C-terminal domain that is very similar to the SH3 domain in the non-catalytic region of nonreceptor tyrosine kinases (including those encoded by the proto-oncogenes c-src and c-abl), in phospholipase C gamma and in alpha-spectrin. We also identified an SH3-related motif in the actin-binding tail domain of myosin-I. The identification of SH3 domains in a family of otherwise unrelated proteins that associate with the membrane cytoskeleton indicates that this domain might serve to bring together signal transduction proteins and their targets or regulators, or both, in the membrane cytoskeleton.     

人核蛋白P68 cDNA基因克隆及全序列测定

靠人合成４个混合聚核苷酸探针，从一个人盘λｇｔ１１ ｃＤＮＡ库筛选到含有ｐ６８ ｃＤＮＡ基因的阳性噬菌斑。经次克隆得到含ｐ６８ ｃＤＮＡ基因的ｐＢＲＢｔ７－ｐ６８质粒。用末端终止法对此ｃＤＮＡ基因进行了全序列测定。分析结构证明得到的ｐ６８ｃＤＮＡ基因含有２２８７３个苷酸，具有一个可阅读框架，共编码６１４个氨基酸。其５＇端非编码区含有１３０个碱基。３＇端非编码区含有３１５个碱基，比已发表的３＇端非