Search results for "Enhancer Elements"
showing 10 items of 35 documents
Structural and functional characterization of a transcription-enhancing sequence element in the rbcL gene of the Chlamydomonas chloroplast genome.
2002
The structure and function of a transcription-enhancing sequence element in the coding region of the Chlamydomonas reinhardtii rbcL gene was analyzed in Chlamydomonas chloroplast transformants in vivo. The enhancer sequence is contained within a DNA segment extending from position +108 to position +143, relative to the start site of rbcL gene transcription. The sequence remains functional when inverted or when placed 34 bp closer to or 87 bp further downstream of the basic rbcL promoter. However, it does not function from a site about 250 bp downstream of its original location. Besides promoting transcription initiation from the rbcL promoter, the element is able to augment transcription fr…
Murine Cytomegalovirus Major Immediate-Early Enhancer Region Operating as a Genetic Switch in Bidirectional Gene Pair Transcription
2007
ABSTRACT Enhancers are defined as DNA elements that increase transcription when placed in any orientation relative to a promoter. The major immediate-early (MIE) enhancer region of murine cytomegalovirus is flanked by transcription units ie1/3 and ie2 , which are transcribed in opposite directions. We have addressed the fundamental mechanistic question of whether the enhancer synchronizes transcription of the bidirectional gene pair (synchronizer model) or whether it operates as a genetic switch, enhancing transcription of either gene in a stochastic alternation (switch model). Clonal analysis of cytokine-triggered, transcription factor-mediated MIE gene expression from latent viral genomes…
Guanine 6-O-Methylation Pattern within the Dioxin Responsive Element of theCYP1A1 Enhancer Shows Two Critical Guanines for AhR/ARNT Binding
2006
The core-recognition motif for TCDD-liganded AhR/ARNT complex of the dioxin-responsive element (DRE) contains four guanine residues, three on the antisense (5'-T T / A GCGTG-3') and one on the sense (5'-CACGC A / T A-3') strand. It has been reported that, in methylation-protection and methylation-interference assays, the TCDD-liganded AhR/ARNT contacts all four guanine residues. On the other hand, it is known that some anticancer drugs, and various environmental and workplace chemicals, including strongly human carcinogenic nitrosoamines, lead to the highly miscoding 6-O-methylation of guanine. In the present study, we have investigated whether specific methylation of guanine at the 6-O-pos…
In Vivo Replication of Recombinant Murine Cytomegalovirus Driven by the Paralogous Major Immediate-Early Promoter-Enhancer of Human Cytomegalovirus
1999
ABSTRACT Transcription of the major immediate-early (MIE) genes of cytomegaloviruses (CMV) is driven by a strong promoter-enhancer (MIEPE) complex. Transactivator proteins encoded by these MIE genes are essential for productive infection. Accordingly, the MIEPE is a crucial control point, and its regulation by activators and repressors is pertinent to virus replication. Since the MIEPE contains multiple regulatory elements, it was reasonable to assume that specific sequence motifs are irreplaceable for specifying the cell-type tropism and replication pattern. Recent work on murine CMV infectivity (A. Angulo, M. Messerle, U. H. Koszinowski, and P. Ghazal, J. Virol. 72:8502–8509, 1998) has do…
Random, asynchronous, and asymmetric transcriptional activity of enhancer-flanking major immediate-early genes ie1/3 and ie2 during murine cytomegalo…
2001
ABSTRACT The lungs are a major organ site of cytomegalovirus (CMV) pathogenesis, latency, and recurrence. Previous work on murine CMV latency has documented a high load and an even distribution of viral genomes in the lungs after the resolution of productive infection. Initiation of the productive cycle requires expression of the ie1/3 transcription unit, which is driven by the immediate-early (IE) promoter P 1/3 and generates IE1 and IE3 transcripts by differential splicing. Latency is molecularly defined by the absence of IE3 transcripts specifying the essential transactivator protein IE3. In contrast, IE1 transcripts were found to be generated focally and randomly, reflecting sporadic P …
The Drosophila Cystoblast Differentiation Factor, benign gonial cell neoplasm, Is Related to DExH-box Proteins and Interacts Genetically With bag-of-…
2000
Abstract Selection of asymmetric cell fates can involve both intrinsic and extrinsic factors. Previously we have identified the bag-of-marbles (bam) gene as an intrinsic factor for cystoblast fate in Drosophila germline cells and shown that it requires active product from the benign gonial cell neoplasm (bgcn) gene. Here we present the cloning and characterization of bgcn. The predicted Bgcn protein is related to the DExH-box family of RNA-dependent helicases but lacks critical residues for ATPase and helicase functions. Expression of the bgcn gene is extremely limited in ovaries but, significantly, bgcn mRNA is expressed in a very limited number of germline cells, including the stem cells.…
Polymorphism of immunoglobulin enhancer element HS1,2A: allele *2 associates with systemic sclerosis. Comparison with HLA‐DR and DQ allele frequency
2007
OBJECTIVE: To investigate the relationship of the polymorphic enhancer HS1,2 central to the 3' enhancer complex regulatory region (IgH3'EC) of the immunoglobulin heavy chain genes with systemic sclerosis (SSc) disease and compare it with HLA-DR and DQ associations. METHODS: A total of 116 patients with SSc were classified as diffuse (dSSc) or limited (lSSc), and as carriers of antitopoisomerase I (anti-Scl70) or anticentromere (ACA) antibodies. Allele and genotype frequencies were assessed in the population as a whole and in the two major subsets, dSSc and lSSc. The concentration of peripheral blood immunoglobulin levels was also determined and analysed according to the genotypes. RESULTS: …
Promoter activity of the sea urchin (Paracentrotus lividus) nucleosomal H3 and H2A and linker H1 a-histone genes is modulated by enhancer and chromat…
2009
Core promoters and chromatin insulators are key regulatory elements that may direct a transcriptional enhancer to prefer a specific promoter in complex genetic loci. Enhancer and insulator flank the sea urchin (Paracentrotus lividus) alpha-histone H2A transcription unit in a tandem repeated cluster containing the five histone genes. This article deals with the specificity of interaction between the H2A enhancer-bound MBF-1 activator and histone gene promoters, and with the mechanism that leads the H1 transcripts to peak at about one-third of the value for nucleosomal H3 and H2A mRNAs. To this end, in vivo competition assays of enhancer and insulator functions were performed. Our evidence su…
Cross-talk between Different Enhancer Elements during Mitogenic Induction of the Human Stromelysin-1 Gene
1996
Platelet-derived growth factor (PDGF) induces the expression of human stromelysin-1, a matrix metalloproteinase involved in tumor invasion and metastasis. Here it is shown that stromelysin-1 gene induction by PDGF depends on Ras and involves three previously identified promoter elements (the stromelysin-1 PDGF-responsive element (SPRE) site, the two head-to-head polyomavirus enhancer A-binding protein-3 (PEA3) sites, and the activator protein-1 (AP-1) binding site). During mitogenic induction, these responsive elements appear to be organized in two independent transcriptional units, SPRE-AP-1 and PEA3-AP-1, which result from specific element cross-talking. Interestingly, expression of a dom…
Physiological activation of the IgH 3' enhancer in B lineage cells is not blocked by Pax-5.
1996
The mouse 3' enhancer contains a high-affinity binding site for the paired box protein Pax-5. Here, we demonstrate by genomic footprinting that the rat 3' enhancer contains a low-affinity binding site for Pax-5, which is occupied in activated splenic B cells. Thus, binding of Pax-5 to the IgH 3' enhancer appears to be evolutionarily conserved in rodents. Analysis of Pax-5 expression in primary B cells demonstrates that Pax-5 remains expressed after 4 days of lipopolysaccharide (LPS) induction, but is down-regulated in 5-day stimulated cells. Similarly, the expression of Pax-5 is down-regulated in vivo in activated large splenocytes, in contrast to small resting cells. Multimerization of the…