what are the structural features of transcriptional activator and repressor proteins.Give an example of how they work. What are the transcriptional co-activators, and mediator complex?It is based...

what are the structural features of transcriptional activator and repressor proteins.

Give an example of how they work. What are the transcriptional co-activators, and mediator complex?It is based on molecular biology

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misscorvello | High School Teacher | (Level 1) eNoter

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Transcriptional activators are proteins that bind to DNA and stimulate transcription of nearby genes. Most activators enhance RNA polymerase binding (formation of the closed complex) or the transition to the open complex required for initiation of transcription. Most activators interact directly with a subunit of RNA polymerase. Some examples follow:

 

  • Regulation of the arabinose regulation by AraC

     

  • Catabolite repression by cAMP-CRP

 

Coactivators are diverse and multifunctional proteins that act downstream of DNA-binding activators to stimulate transcription. Recent studies elucidate the temporal sequence in which coactivators are recruited to target promoters, and how their enzymatic properties and molecular interactions culminate in transcriptional initiation. Examples:

ACF – ATP-utilizing chromatin assembly and remodeling factor
AD – activation domain
ATM – ataxia telangiectasia mutated
CARM1 – coactivator-associated arginine methyltransferase 1
CATD – cathepsin D
CBP – CREB-binding protein
ChIP – chromatin immunoprecipitation
CREB – cAMP response element binding protein
CTD – carboxy-terminal domain (of RNA pol II)
ER – estrogen receptor
GTF – general transcription factor
HAT – histone acetyltransferase
IFN-β – interferon β
P/CAF – p300/CBP-associated factor
PIC – preinitiation complex
PKA – protein kinase A
PKC – protein kinase C
PRMT1 – protein arginine methyltransferase 1
RNA pol II – RNA polymerase II
SAGA – Spt-Ada-Gcn5-acetyltransferase complex
TAF – TBP-associated factor
TBP – TATA-binding proteinDNA is packed into chromatin and transcriptionis dependent upon activators that recruit other factors toreverse the repressive effects of chromatin. The response toactivators requires additional factors referred to as coactivators.One such coactivator, mediator, is a multi-subunit complex capable of responding to different activators. It plays an keyrole in activation, bridging DNA-bound activators, the generaltranscriptional machinery, especially RNA polymerase II, andthe core promoter. Its subunits are necessary for a varietyof positive and negative regulatory processes and serve asthe direct targets of activators themselves. In vivo and invitro studies support various roles for mediator in transcriptioninitiation, while structural studies demonstrate that it engagesin multiple interactions with RNA polymerase II, and adoptsconformations that are activator specific.
This information was all available from research articles obtained through bridgew.edu's library; accessible only for students.

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