Upstream activating sequence: Difference between revisions

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An '''upstream activation sequence''' (UAS) is a [[Cis-regulatory element|cis-acting regulatory sequence]]. It is distinct from the [[promotor (biology)|promoter]] and increases the [[Transcription (genetics)|expression]] of a neighbouring [[gene]]. Due to its essential role in activating transcription, the upstream activating sequence is often considered to be analogous to the function of the [[Enhancer (genetics)|enhancer]] in multicellular eukaryotes. <ref>{{cite journal|last1=Webster|first1=Nocholas|last2=Jin|first2=Jia Rui|last3=Green|first3=Stephen|last4=Hollis|first4=Melvyn|last5=Chambon|first5=Pierre|title=The Yeast UAS{{sub|G}} is a transciptional enhancer in human hela cells in the presence of the GAL4 trans-activator|journal=Cell|date=29 January 1988|volume=52|issue=2|pages=169-178}}</ref>. Upstream activation sequences are a crucial part of induction, enhancing the expression of the enzyme of interest through increased transcriptional activity. <ref>{{cite journal|last1=West, Jr.|first1=Robert W.|last2=Yocum|first2=R. Rogers|last3=Ptashne|first3=Mark|title=''Saccharomyces cerevisiae'' GAL1-GAL10 Divergenet Promoter Region: Location and Function of the Upstream Activating Sequence UAS{{sub|G}}|journal=Mollecular and Cellular Biology|date=November, 1984|volume=4|issue=11|pages=2467-2478}}</ref>. The upstream activation sequence is found adjacently upstream to a minimal promoter (TATA box) and serves as a binding site for transactivators. If the transcriptional transactivator does not bind to the UAS in the proper orientation then transcription cannot begin. <ref>{{cite journal|last1=Lewandoski|first1=Mark|title=Conditional control of gene expression in the mouse|journal=Nature Reveiws Genetics|date=October, 2001|volume=2|pages=743-755}}</ref>. To further understand the function of an upstream activation sequence, it is beneficial to see its role in the cascade of events that lead to transcription activation. The pathway begins when activators bind to their target at the UAS recruiting a [[mediator (coactivator)|mediator]]. A TATA-binding protein subunit of a [[transcription factor]] then binds to the [[TATA box]], recruiting additional transcription factors. The mediator then recruits [[RNA polymerase II]] to the pre-initiation complex. Once initiated, RNA polymerase II is then released from the complex and transcription begins. <ref>{{cite journal|last1=Wion|first1=Didier|last2=Casadesus|first2=Josep|title=N{{sup|6}}-methyl-adenine: An epigenetic signal for DNA-protein interactions|journal=Nature Reviews Microbiology|date=March, 2006|volume=4|pages=183-192|doi=10.1038/nrmicro1350}}</ref>

==Examples of Upstream Activation Sequences==