Upstream activator elements

The core promoter module can be defined functionally by its capability to assemble the transcription initiation complex (see Figure 4.3) and orient it specifically towards the TSS of the promoter [13], defining the exact location of the TSS. Various combinations of about four distinguishable core promoter elements that constitute a general core promoter can achieve this. This module includes the TATA box, the initiator region (INR), an upstream activating element, and a downstream element. (The TATA box is a basic... 

Activator proteins (and a few repressors) are important in eukaryotes, as they are in prokaryotes. The DNA sequences to which activator proteins bind in eiikaryotic DNA are called response elements. A few response elements are located within the promoter region (upstream promoter elements [UPE]), but most are outside the promoter and often clustered to form an enhancer region that allows control of gene expression by multiple signals (Figure 1-5-4). 

An increase in the basal transcription activity originating from the promoter requires regulatory DNA sequences. These sequences can be proximally or distaUy located and serve as binding sites for transcriptional activators. The cis-acting DNA elements can be found near the promoter in either orientation. They are often termed upstream activating sequences" (UAS). Regulatory sequences can also be located far from the promoter. Their effect is independent of their orientation and they are known as enhancers. 

Fig. 1.30. Structure of a typical eucaryotic transcription start site. Enhancer elements and UAS elements (UAS upstream activating sequences) are binding sites for positive and negative regulatory DNA-binding proteins. The TATA box is the binding site for the TATA box binding protein (TBP) and serves to position the RNA polymerase holoenzyme on the promoter. For promoters that do not possess a TATA box, this function is fulfilled by an initiator region.

Found Regulatory Elements in Promoters and Upstream Activator Sites... 

Cis elements involved in transcription in yeast (a) and in vertebrates (b). Upstream activator sequences (UAS) in yeast are similar in function to upstream enhancers in vertebrates. Yeast has no parallel to downstream enhancers found in vertebrates. 

Two different types of membrane-based osmosensors have been proposed for animal cells extracellular solute sensors and membrane stretch-activated sensors. The former sensors are conjectured to function by detecting changes in the concentration of specific ions, for instance, sodium ion, in the external fluids. There is some indirect evidence for sodium-specific sensors in animal cells, and sodium-gated cation channels have been proposed as candidates for this role. However, no direct evidence for their involvement as upstream osmoregulatory elements has yet been presented. 

Bachhawat, N., Ouyang, Q., and Henry, S.A., 1995, Functional characterization of an inositol-sensitive upstream activation sequence in yeast A c/,v-regulatory element responsible for inositol-choline mediated regulation of phospholipid biosynthesis. J. Biol. Chem. 270 25087-25095. 

The activities of many promoters in higher eukaryotes are greatly increased by another type of cis-acting element called an enhancer. Enhancers sequences have no promoter activity of their own yet can exert their stimulatory actions over distances of several thousand base pairs. They can be upstream, downstream, or even in the midst of a transcribed gene. Moreover, enhancers are effective when present on either DNA strand (equivalently, in either orientation). Enhancers in yeast are known as upstream activator sequences (UASs). 

TATA box is the first step in the assembly of the RNA polymerase II transcription complex. The frequency of transcription initiation is often affected by binding certain transcription factors to upstream elements such as the CAAT box and the GC box. The activity of many promoters is affected by enhancers, regulatory sequences that may occur thousands of base pairs upstream or downstream of the gene they affect. (In yeast these sequences are called upstream activator sequences, or UAS.) The effects of enhancers can be complex. For example, a single gene may be controlled by the combined activities of several enhancers. Hormone response elements (Section 16.4) often act as enhancers. 

A detailed functional analysis of the immunoglobulin promoter elements is not available. However, comparison of sequences from a number of immunoglobulin promoters revealed the presence of a well-conserved octanucleotide consensus (ATGCAAAT) in all VH promoters and its complement (ATTTGCAT) in all VL promoters as well as in the heavy chain enhancer [54,55], This octanucleotide has been shown to be essential for transcription in both VH and VK promoters, as deletion of it abolishes promoter activity [46,55,56]. Furthermore, in the presence of the IgH enhancer, the octanucleotide is a sufficient VH upstream promoter element as measured in transfection assays [57],... 

The S. cerevisiae genome contains regulatory elements called upstream activating sequences (UASs), which function... 

MAT locus (in yeast) 471 mediator 471 nuclear receptors 464 promoter 449 promoter-proximal elements 455 repression domain 462 repressors 449 RNA polymerase II 450 silencer sequences 472 TATA box 454 upstream activating sequences (UASs) 457 yeast two-hybrid system 480 zinc finger 463... 

Found Regulatory Elements in Promoters and Upstream Activator Sites. Table 28-2 Functional Qassificafion of Positive-... 

Eukaryotes have different RNA polymerase-binding promoter sequences than prokaryotes. The TATA consensus sequence of the eukaryotic promoter region is located 25 to 35 bp upstream from the transcription start site (Fig. 6.13). The low activity of basal promoters is greatly inaeased by the presence of other elements located upstream from the promoter called upstream regulatory elements. These elements are located 40 to 200 bp upstream of the promoter sequence and include the SP1 box, the CCAAT box, and the hormone response elements. Transcription from many eukaryotic promoters can be stimulated by control elements, called enhancers, located many thousands of base pairs away from the transcription start site and usually 100 to 200 bp in length. 

The active element serves as a transcription factor for a reporter gene (e.g. P-galactosidase of lacZ) or prototropic marker (e.g. HIS5, ADEZ) that are under the control of upstream activating sequence (UAS) recognized by BD. Thus only those transformants... 

Other biological events that can be assayed on micrographs of individual active genes are the effects of upstream control elements on transeription, the role of specific transcribed sequences in dictating the formation of RNP structures, and the role of specific trans-acting factors in dictating the formation of RNP structure. Each of these will be considered briefly in the following review of our recent applications. 

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