lecture 13 - Lecture13 , theholoenzyme, . where

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Lecture 13 In prokaryotic transcription, it is easy to recognize the length of the promoter and con- sensus sequences in the promoter the holoenzyme, which is the core enzyme 2 ’ and are responsible for recogniz α ββ σ - ing the consensus sequence at the -35 and -10. The -35 is for binding the DNA and -10 is where the helix has to melt In eukaryotic transcription, involves RNA polymerases. The polymerases still have to start transcription at the promoter. The promoter has to be asymmetric so that the binding is asymmetric so that it knows which is the template strand and which is the coding strand. The RNA polymerase in eukaryotes do not directly recognize the promoter, they don’t have affinity for DNA have two subunits that are homologues, the and ’ subunits of prokaryotic poly β β - merases that bind the nucleotides and are involved in catalysis. in eukaryotic transcription, there are many more diverse genes, many more diverse promoter. The role of binding promoter is left to TFs. These are proteins that are not subunits of RNA polymerase, but they are factors that are responsible for recognizing promoter elements. the limit of the promoter usually involve empirical information, where by you take larger sequences surrounding the gene of interest and try shortening this fragment and see what will support transcription in a normal level find that instead of having one consensus sequence, the promoters are built of many consensus sequence, each of which bind many factors. These factors are called basal factors basal factors - minimum required to initiate transcription in euka- ryotes. some of these factors directly recruit the RNA polymerase to the start point of transcription If you have just basal factors, transcription would occur at such a low level that transcription would not be detected. there are many other factors either called activators, these activators bind sequences of the promoter that are either upstream of the start point, or way up or downstream called enhancers have many factors involved in recruiting the polymerase sequences necessary for transcription in eukaryotes can take up to 30,000 bases or can even be a million bases away from where transcrip- tion begins. Making it difficult to clone a gene and put it so an affected promoter adjacent to a transfected cell, because the sequences neces- sary for proper transcription include such a large amount of DNA and such a great distance from where transcription begins can have two types of genes that are transcribed: those that are not regulated and are constitutively expressed constitutive - genes are on all the time, some times they are called house keep- ing genes regardless of their role in the cell because they are not regulated
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those genes have these short consensus sequences that are bound by factors that would be found in all cells. The cis acting consensus sequences to initiate the initiation of transcription
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lecture 13 - Lecture13 , theholoenzyme, . where

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