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A typical operon. In genetics, an operon is a functioning unit of DNA containing a cluster of genes under the control of a single promoter. [1] The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo splicing to create monocistronic mRNAs that are translated separately, i.e. several strands of mRNA that each encode a single gene product.
Depending on the metabolic conditions, the attenuator either stops transcription at that point or allows read-through to the structural gene part of the mRNA and synthesis of the appropriate protein. Attenuation is a regulatory feature found throughout Archaea and Bacteria causing premature termination of transcription . [ 2 ]
The gene trpP plays a role in trp transportation, while the gene trpG is utilized in the folate operon, and the gene ycbK is involved in synthesis of an efflux protein. The activated TRAP protein is regulated by an anti-TRAP protein and AT synthesis. AT can inactive TRAP to lower the transcription of tryptophan. [21]
These mechanisms include control over protein localization or control over whether the protein can bind DNA. [32] An example of this is the protein HSF1, which remains bound to Hsp70 in the cytosol and is only translocated into the nucleus upon cellular stress such as heat shock. Thus the genes under the control of this transcription factor ...
The promoter is recognized by RNA polymerase and an associated sigma factor, which in turn are often brought to the promoter DNA by an activator protein's binding to its own DNA binding site nearby. In eukaryotes The process is more complicated, and at least seven different factors are necessary for the binding of an RNA polymerase II to the ...
Regulation of gene expression by a hormone receptor Diagram showing at which stages in the DNA-mRNA-protein pathway expression can be controlled. Regulation of gene expression, or gene regulation, [1] includes a wide range of mechanisms that are used by cells to increase or decrease the production of specific gene products (protein or RNA).
One method through which this happens is the DnaA protein. DnaA is a protein which recognises the origin of replication, promotes a local unwinding of an AT rich DNA region and finally guides the helicase DnaB to its entry site. DnaA is the replication initiation factor which causes DNA replication if present in sufficient concentration. [5]
TFIIH is a ten-subunit protein, including both ATPase and protein kinase activities. [18] While the upstream promoter DNA is held in a fixed position by TFIID, TFIIH pulls downstream double-stranded DNA into the cleft of the polymerase, driving the separation of DNA strands and the transition of the preinitiation complex from the closed to open ...