The retinoblastoma susceptibility gene encodes a nuclear phosphoprotein associated with DNA binding activity

The human gene (RB) that determines susceptibility to hereditary retinoblastoma has been identified recently by molecular genetic techniques. Previous results indicate that complete inactivation of the RB gene is required for tumour formation. As a 'cancer suppressor' gene, RB thus functions in a manner opposite to that of most other oncogenes. Sequence analysis of RB complementary DNA clones demonstrated a long open reading frame encoding a hypothetical protein with features suggestive of a DNA-binding function. To further substantiate and identify the RB protein, we have prepared rabbit antisera against a trypE-RB fusion protein. The purified anti-RB IgG immunoprecipitates a protein doublet with apparent relative molecular mass (Mr) of 110,000-114,000. The specific protein(s) are present in all cell lines expressing normal RB mRNA, but are not detected in five retinoblastoma cell lines examined. The RB protein can be metabolically labelled with 32P-phosphoric acid, indicating that it is a phosphoprotein. Biochemical fractionation and immunofluorescence studies demonstrate that the majority of the protein is located within the nucleus. Furthermore, the protein can be retained by and eluted from DNA-cellulose columns, suggesting that it is associated with DNA binding activity. Taken together, these results imply that the RB gene product may function in regulating other genes within the cell.     

Isolation of tomato proteinase inhibitor II gene and the function of its intron

The genomic DNA sequence of tomato proteinase inhibitor II gene (named tin2i, whose accession number in GenBank is AF007240) was isolated by PCR techniques. The intron sequence (TPI), with a length of 109 bp, owns typical structures of GT/AG dinucleotides at both ends and high content of AT base pairs which accounts for 80.7% of the total nucleotides. As shown by recombination experiment, the TPI sequence could efficiently promote the expression of the reporter gene gusA and this effect was independent of the position and orientation of the intron, thus showing its role as an enhancer. Such experiments as gel retardation assays, GUS histochemical staining and GUS fluorometric assays further demonstrated that TPI sequence maybe has promoter-like activity.     

Coat protein gene and 3′ non-coding region of tobacco mosaic virus and tomato mosaic virus are associated with viral pathogenesis in Nicotiana tabacum

The camellia isolate of tomato mosaic virus (ToMV-TL) can induce local necrotic lesions on the inoculated leaves in Nicotiana tabacum, whereas the broad bean isolate of tobacco mosaic virus (TMV-B) produces the mosaic symptom on systemic leaves. To examine viral determinant for differential infection phenotype in N. tabacum, the coat protein gene and the 3′ non-coding region of TMV was replaced with that of ToMV, the chimeric virus induced similar local necrotic lesions to that induced by ToMV. The results indicate that the coat protein gene and the 3′ non-coding region of TMV and ToMV influence the virus-induced pathogenesis in N. tabacum.     

小麦中与低脱氧雪腐镰刀菌烯醇含量关联的抗性基因类似物

脱氧雪腐镰刀菌烯醇(Deoxynivalenol,DON)是小麦遭受赤霉病危害后由赤霉病菌———禾谷镰刀菌产生的一种真菌毒素,这种毒素对人类和家畜的健康产生危害,严重地影响小麦的利用价值.种植低DON含量的品种是减少这种毒素危害的有效措施,而分子标记辅助育种技术能加速低DON品种的选育进程.在采用AFLP、SSR分子标记的基础上,进一步利用抗性基因类似物(RGA)对‘宁7840’(低DON含量的品种)和‘Clark’(高DON含量的品种)建立的133个重组自交系进行了DON含量的遗传特性分析.研究结果发现两个DON含量的数量特性位点(QTL),它们中含有4个与低DON含量密切相关RGAs,其中三个RGAs(RGA14-1,RGA16-1,RGA18-1)座落在染色体1A的长臂上,另一个(RGA14-2)座落在染色体5B的长臂上.座落在1AL和5BL上的QTL分别解释16.81%和7.84%的DON含量变异.DNA序列分析表明这些RGAs均与现已发现的抗性基因同源/类似,它们可能在小麦的低DON含量和赤霉病抗性上扮演着重要的角色.     

衣藻的核基因组转化及外源基因转录分析

通过珠磨法将衣藻表达载体pSP108转入到莱茵衣藻细胞壁缺陷型CC-400藻株中,经抗性筛选及PCR鉴定,获得了24个转化藻株.在抗性基因ble编码序列的中间部位和末端部位分别设计两对不同的探针引物,运用实时荧光定量PCR对转基因藻株进行外源基因转录水平的分析.结果发现:不同转化藻株外源基因的转录水平有明显差异;同一转化藻株两对探针引物,外源基因的转录水平也存在差异.说明莱茵衣藻在转化过程中,外源基因整合到基因组上的片段数量及片段长度和完整性具有不确定性.     

Conservation between yeast and man of a protein associated with U5 small nuclear ribonucleoprotein

The process of nuclear pre-messenger RNA splicing is similar in Saccharomyces cerevisiae and metazoan cells in that the two-step mechanism is identical and the reaction occurs in a large ribonucleoprotein complex, the spliceosome. Little is known, however, about the degree of conservation of splicing factors other than of the small nuclear RNAs (snRNAs). Yeast counterparts of the metazoan spliceosomal snRNAs (U1, U2, U4, U5 and U6) have been identified but, with the exception of U6, the yeast snRNAs are larger and sequence similarity is limited to short regions. By using antibodies against the yeast PRP8 protein, a pre-mRNA splicing factor of relative molecular mass 280,000 (Mr280K) stably associated with U5 small nuclear ribonucleoproteins (snRNPs), we have now identified an immunologically related protein in HeLa cell nuclear extracts. The HeLa cell protein has an Mr greater than 200K and is associated with purified 20S U5 snRNPs. This is the first report of phylogenetic conservation between yeast and man of a protein splicing factor.     

A gene in the human major histocompatibility complex class II region controlling the class I antigen presentation pathway

Major histocompatibility complex (MHC) class I molecules export peptides to the cell surface for surveillance by cytotoxic T lymphocytes. Intracellular peptide binding is critical for the proper assembly and transport of class I molecules. This mechanism is impaired as a result of a non-functional peptide supply factor gene (PSF) in several human mutant cell lines with genomic lesions in the MHC. We have now identified PSF in the MHC class II region by deletion mapping in mutants and chromosome-walking. PSF is homologous to mammalian and bacterial ATP-dependent transport proteins, suggesting that it operates in the intracellular transport of peptides.