Difference between revisions of "Promoters/Overview"

(New page: right The registry has a large collection of Promoters available. We categorize promoters in two ways. First, most promoters are designed for...)
 
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[[Image:ConstitutivePromoter.png|200px|right]]
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[[Image:PromoterIconBC.png|thumb|right|400px|The regsitry symbol for a promoter is shown above a typical sequence for a bacterial promoter.  The lavender shaded boxes indicate the two most conserved regions of a bacterial promoter and are located at -10 and -35 bases from the transcriptional start site (shaded in green).  There are, on average, 17bp between the -10 and -35 sites and 7bp between the -10 site and the transcriptional start site <cite>pribnow</cite><cite>harley</cite><cite>lisser1</cite><cite>lisser2</cite>.]]
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The registry has a large collection of [[Promoters]] available.  We categorize promoters in two ways.  First, most promoters are designed for a particular RNA polymerase (RNAP) holoenzyme, e.g ''E. coli'' RNAP bound to a particular &sigma; factor (a &sigma; factor is a protein that confers specificity on ''E. coli'' RNAP for particular promoter sequences), or the RNAP from the T7 bacteriophage. Second, promoters are categorized by the manner in which they are regulated.  For example a promoter may be unregulated (constitutive), positively regulated (activatable) or negatively regulated (repressible).  Regulated promoters allow you to "program" biological systems.  For example, you can perform logic (e.g. "If protein X is present, promoter Y is off") or ensure that a particular gene is only expressed when a particular small molecule is present in the media.
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A promoter is a DNA sequence that tends to recruit transcriptional machinery and lead to transcription of the downstream DNA sequence. The specific sequence of the promoter determines the binding affinity of the transcriptional machinery for the promoter and how likely the transcriptional machinery is to initiate transcription after being recruited to the DNA.  A "strong" promoter is one that leads to a high rate of transcription initiation, while a "weak" promoter leads to a low rate of transcription initiation.   
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In addition to sequences that "promote" transcription, a promoter may include additional sequences known as operators that control the strength of the promoter.  For example, a promoter may include a binding site for a protein that either attracts or obstructs the transcriptional machinery from binding to the promoter.  The presence or absence of the protein will affect the strength of the promoter.  Such a promoter is known as a regulated promoter. 
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The Registry has a large collection of promoters both unregulated and regulated.  Most of our promoters are designed to be recognized by ''E. coli'' RNA polymerase but we also have several promtoers that are recognized by T7 RNA polymerase and other RNA polymerase holoenzymes.

Revision as of 03:10, 2 February 2009

The regsitry symbol for a promoter is shown above a typical sequence for a bacterial promoter. The lavender shaded boxes indicate the two most conserved regions of a bacterial promoter and are located at -10 and -35 bases from the transcriptional start site (shaded in green). There are, on average, 17bp between the -10 and -35 sites and 7bp between the -10 site and the transcriptional start site pribnowharleylisser1lisser2.

A promoter is a DNA sequence that tends to recruit transcriptional machinery and lead to transcription of the downstream DNA sequence. The specific sequence of the promoter determines the binding affinity of the transcriptional machinery for the promoter and how likely the transcriptional machinery is to initiate transcription after being recruited to the DNA. A "strong" promoter is one that leads to a high rate of transcription initiation, while a "weak" promoter leads to a low rate of transcription initiation.

In addition to sequences that "promote" transcription, a promoter may include additional sequences known as operators that control the strength of the promoter. For example, a promoter may include a binding site for a protein that either attracts or obstructs the transcriptional machinery from binding to the promoter. The presence or absence of the protein will affect the strength of the promoter. Such a promoter is known as a regulated promoter.

The Registry has a large collection of promoters both unregulated and regulated. Most of our promoters are designed to be recognized by E. coli RNA polymerase but we also have several promtoers that are recognized by T7 RNA polymerase and other RNA polymerase holoenzymes.