共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
3.
4.
5.
6.
7.
Functional RNA polymerase II promoters in solitary retroviral long terminal repeats (LTR-IS elements). 总被引:4,自引:2,他引:2
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
LTR-IS elements are middle repetitive sequences in the mouse genome with structural features of solitary retroviral LTRs. In order to get some insight in the possible functional role of these sequences the promotor activity of two LTR-IS representatives differing by 105 bp in their U3 region was investigated. Gene fusions between LTR-IS sequences and the bacterial gene coding for chloramphenicol acetyl transferase (CAT) were transfected into mouse 3T6 cells and the expression of CAT was measured. It is shown that the LTR-IS sequences represent weak RNA polymerase II promoters which require enhancement by cis-or trans-activating factors. 相似文献
8.
Alu and L1 retroelements have been suggested to initiate the spread of CpG methylation. In this study, the spread of CpG methylation was estimated based on the distance between the CpG islands and the nearest retroelements. All human genes (23,116) were examined and the correlations between the length of the CpG islands and the distance and density of the confronting retroelements were examined using nonoverlapping 5-kb windows. There was a linear relationship between the length of the CpG islands and the density of the Alu elements and an inverse relationship between the CpG islands and the L1 elements located more distantly, suggesting a suppressive effect of the Alu's on the spread of L1 methylation. Methylation analysis of the transitional CpG sites between the CpG islands and the nearest retroelements upstream of 16 genes was then carried out using DNA preparations from 11 different human tissues. Methylation-variable transitional CpGs were observed for the selected genes and the different tissues. 相似文献
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
We describe a direct procedure for screening genomic recombinant DNA libraries or restriction fragments of cloned DNA regions for RNA polymerase II promoters. Cellular polyadenylated mRNA is chemically de-capped by beta-elimination reaction and enzymatically re-capped with [alpha-32P]GTP by vaccinia guanylyl transferase. Since this enzyme only accepts di- or triphosphorylated 5' termini as a substrate, the mRNAs are labeled exclusively at the first nucleotide, irrespective of whether the mRNA was intact or fragmented before in vitro capping. By using in vitro-capped mRNA as a hybridization probe, recombinant DNA molecules or restriction fragments that carry a cap site (and thus likely an RNA polymerase II promoter) can directly be identified. Here, we demonstrate the applicability of this procedure by the isolation and characterization of several genomic DNA clones containing RNA polymerase II promoter sequences, that are highly active in liver. 相似文献
19.