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Gene promoters are typically located upstream of the gene and can have regulatory elements several kilobases away from the transcriptional start site (enhancers). In eukaryotes, the transcriptional complex can cause the DNA to bend back on itself, which allows for placement of regulatory sequences far from the actual site of transcription.
In eukaryotic cells the structure of the chromatin complex of DNA is folded in a way that functionally mimics the supercoiled state characteristic of prokaryotic DNA, so although the enhancer DNA may be far from the gene in a linear way, it is spatially close to the promoter and gene.
The promoter is where RNA polymerase, the enzyme that copies the genetic sequence and synthesizes the mRNA, attaches to the DNA strand. Some genes are modulated by activators, which have the opposite effect on gene expression as repressors. Inducers can also bind to activator proteins, allowing them to bind to the operator DNA where they ...
Methods to study promoter activity commonly are based in the expression of a reporter gene from the promoter of the gene of interest. [16] [2] [17] Mutations and deletions are made in a promoter region, and their changes on couple expression of the reporter gene are measured. [18] The most important reporter genes are the fluorescence proteins ...
In eukaryotes, genes tend to be transcribed individually, and each gene is controlled by its own regulatory sequences. [2] Regulatory sequences where activators bind are commonly found upstream from the promoter, but they can also be found downstream or even within introns in eukaryotes. [1] [2] [3]
Catalytic inhibitors are the other main identification of TopII inhibitors. Common catalytic inhibitors are Bisdioxopiperazine compounds and sometimes act competitively against TopII poisons. They function to target enzymes inside the cell thus inhibiting genetic processes such as DNA replication, and chromosome dynamics. [76]
Promoter-dependent silencers are understood to be silencer elements because they are position and orientation-dependent but must also use a promoter-specific factor. [5] There has been a recent discovery of Polycomb-group Response Elements (PREs), which can allow and inhibit repression depending on the protein bound to it, and the presence of ...
Since then, researchers have established that the E-box affects gene transcription in several eukaryotes and found E-box binding factors that identify E-box consensus sequences. [9] In particular, several experiments have shown that the E-box is an integral part of the transcription-translation feedback loop that comprises the circadian clock .