共查询到20条相似文献,搜索用时 10 毫秒
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Characterization of long terminal repeat sequences of HTLV-III 总被引:30,自引:0,他引:30
B Starcich L Ratner S F Josephs T Okamoto R C Gallo F Wong-Staal 《Science (New York, N.Y.)》1985,227(4686):538-540
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The functional activity of the promoter unit contained within the long terminal repeat (LTR) of bovine leukemia virus (BLV) was examined by monitoring transient expression of a heterologous gene placed under its control. Various cell lines were transfected with recombinant plasmids carrying the bacterial chloramphenicol acetyltransferase (CAT) gene coupled to the BLV LTR (pBL-cat). Transient expression of CAT activity directed by the BLV LTR was observed only in the established BLV-producer cell lines derived from fetal lamb kidney (FLK) cells and bat lung cells. The amount of CAT activity transiently expressed in FLK-BLV cells was decreased approximately tenfold by deletion of LTR sequences located within a region 100 to 170 nucleotides upstream of the RNA start site. Surprisingly, removal of the region 50 base pairs downstream of the RNA initiation site to the 3'-end of the LTR reduced the expression of CAT activity by 87 percent. The BLV LTR thus appears to be an unusual promoter unit, functioning in a cell type-specific manner and possessing sequences on both the 5' and 3' sides of the RNA start site that influence gene expression. 相似文献
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The pX protein of HTLV-I is a transcriptional activator of its long terminal repeats 总被引:120,自引:0,他引:120
B K Felber H Paskalis C Kleinman-Ewing F Wong-Staal G N Pavlakis 《Science (New York, N.Y.)》1985,229(4714):675-679
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To begin to understand the genetic architecture of natural variation in gene expression, we carried out genetic linkage analysis of genomewide expression patterns in a cross between a laboratory strain and a wild strain of Saccharomyces cerevisiae. Over 1500 genes were differentially expressed between the parent strains. Expression levels of 570 genes were linked to one or more different loci, with most expression levels showing complex inheritance patterns. The loci detected by linkage fell largely into two categories: cis-acting modulators of single genes and trans-acting modulators of many genes. We found eight such trans-acting loci, each affecting the expression of a group of 7 to 94 genes of related function. 相似文献
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长末端重复序列(LTR)反转录转座子广泛存在于植物基因组中,本质是一段可移动的脱氧核糖核酸(DNA)序列。大多数LTR反转录转座子在外界环境变化下能够被激活转录,对环境变化做出响应。为研究毛竹基因组中的LTR反转录转座子的转录活性及在非生物环境胁迫下表达量的具体变化,克隆和鉴定了1个毛竹Phyllostachys edulis反转录转座子PHRE7。该转座子全长为6 073 bp,属于Ty1-copia家族中的Tork分支,LTR序列相似性为96.7%,插入时间为126.923万a前。对毛竹实生苗分别进行辐照(30,50,70 Gy),甲基化抑制剂(50,100,150 μmol·L-1),高温(42℃),低温(4℃),高盐(0.1,0.2,0.3 mol·L-1)等5种不同胁迫处理,通过定量荧光聚合酶链式反应(PCR)检测,PHRE7在INT,RT和RH等3个结构域中的表达量仅在辐照及0.2~0.3 mol·L-1高盐处理下随处理强度的上升而下降,其余所有处理(甲基化抑制剂、高温、低温、高盐0.1~0.2 mol·L-1)的表达量都随处理强度呈上升趋势。这些结果表明:PHRE7转座子是一个具有转录活性的LTR反转录转座子,且外界非生物环境胁迫对其表达模式有较大影响,表明PHRE7转座子能够响应外界环境变化。 相似文献
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【目的】从苹果基因组中分离微型反向重复转座元件(MITE),研究其对苹果基因组进化的作用。【方法】利用PIF转座酶简并引物扩增苹果PIF转座酶基因,采用染色体步移技术获得PIF转座酶基因的未知侧翼序列,使用EMBOSS的Eiverted软件查找靶位点重复(target site duplication,TSD)和末端反向重复(terminal inverted repeat,TIR)序列。【结果】苹果MITEs拥有MITEs的典型特征,包括长度短,不具有潜在的编码能力,富含A+T,易插入非编码区,有TIRs和TSDs,有形成二级结构的可能。【结论】苹果MITEs属于Tourist家族,与苹果PIF DNA转座子相关;苹果MITEs与基因相连,在基因调节上起重要作用;苹果MITEs具有潜在的转座能力,对苹果遗传多样性、进化及育种有重要作用。 相似文献
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Two different cis-active elements transfer the transcriptional effects of both EGF and phorbol esters 总被引:27,自引:0,他引:27
H P Elsholtz H J Mangalam E Potter V R Albert S Supowit R M Evans M G Rosenfeld 《Science (New York, N.Y.)》1986,234(4783):1552-1557
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Paprotka T Delviks-Frankenberry KA Cingöz O Martinez A Kung HJ Tepper CG Hu WS Fivash MJ Coffin JM Pathak VK 《Science (New York, N.Y.)》2011,333(6038):97-101
The retrovirus XMRV (xenotropic murine leukemia virus-related virus) has been detected in human prostate tumors and in blood samples from patients with chronic fatigue syndrome, but these findings have not been replicated. We hypothesized that an understanding of when and how XMRV first arose might help explain the discrepant results. We studied human prostate cancer cell lines CWR22Rv1 and CWR-R1, which produce XMRV virtually identical to the viruses recently found in patient samples, as well as their progenitor human prostate tumor xenograft (CWR22) that had been passaged in mice. We detected XMRV infection in the two cell lines and in the later passage xenografts, but not in the early passages. In particular, we found that the host mice contained two proviruses, PreXMRV-1 and PreXMRV-2, which share 99.92% identity with XMRV over >3.2-kilobase stretches of their genomes. We conclude that XMRV was not present in the original CWR22 tumor but was generated by recombination of two proviruses during tumor passaging in mice. The probability that an identical recombinant was generated independently is negligible (~10(-12)); our results suggest that the association of XMRV with human disease is due to contamination of human samples with virus originating from this recombination event. 相似文献
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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. 相似文献
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Santiago ML Montano M Benitez R Messer RJ Yonemoto W Chesebro B Hasenkrug KJ Greene WC 《Science (New York, N.Y.)》2008,321(5894):1343-1346
Recovery from Friend virus 3 (Rfv3) is a single autosomal gene encoding a resistance trait that influences retroviral neutralizing antibody responses and viremia. Despite extensive research for 30 years, the molecular identity of Rfv3 has remained elusive. Here, we demonstrate that Rfv3 is encoded by Apobec3. Apobec3 maps to the same chromosome region as Rfv3 and has broad inhibitory activity against retroviruses, including HIV. Not only did genetic inactivation of Apobec3 convert Rfv3-resistant mice to a susceptible phenotype, but Apobec3 was also found to be naturally disabled by aberrant messenger RNA splicing in Rfv3-susceptible strains. The link between Apobec3 and neutralizing antibody responses highlights an Apobec3-dependent mechanism of host protection that might extend to HIV and other human retroviral infections. 相似文献
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Kane M Case LK Kopaskie K Kozlova A MacDearmid C Chervonsky AV Golovkina TV 《Science (New York, N.Y.)》2011,334(6053):245-249
To establish chronic infections, viruses must develop strategies to evade the host's immune responses. Many retroviruses, including mouse mammary tumor virus (MMTV), are transmitted most efficiently through mucosal surfaces rich in microbiota. We found that MMTV, when ingested by newborn mice, stimulates a state of unresponsiveness toward viral antigens. This process required the intestinal microbiota, as antibiotic-treated mice or germ-free mice did not transmit infectious virus to their offspring. MMTV-bound bacterial lipopolysaccharide triggered Toll-like receptor 4 and subsequent interleukin-6 (IL-6)-dependent induction of the inhibitory cytokine IL-10. Thus, MMTV has evolved to rely on the interaction with the microbiota to induce an immune evasion pathway. Together, these findings reveal the fundamental importance of commensal microbiota in viral infections. 相似文献