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Review3-4 - FullReviewSheet(34 Monday,June02,2008 6:20PM...

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Full Review Sheet (3-4) Monday, June 02, 2008 6:20 PM Lecture 3   Transcription Regulation   Difference between Prokaryotic and Eukaryotic transcription regulation  - prokaryotic  default is transcription 'on' and needs a repressor to turn it off, whereas eurkaryotic default is  'off' and needs activators and transcription factors to turn it 'on'.  Promoter Proximal Elements  - precede the promoter up to 200bp away, and bind factors that  affect many genes that eventually promote transcription, some elements are more important  than others Yeast Transcription Pathway (Gal Pathway)  - yeast only produces enzymes for galactose  metabolism when galactose is present, unlike operons, the enzymes required for galactose  metabolism is located on various chromosomes and are not adjacent to one another,  Gal 4  - a transcription activator protein in Yeast that binds to UAS (upstream activator  sequence), recruits co-activators (mediator complex) and TFII and has 2 domains, the DNA  binding domain and the activation domain, these domains can be mixed and matched in  different organisms and still maintain activity: Gal 4 can only work when Gal80 is NOT bound  to it Gal 80  - protein that binds to Gal4 by default and prevents the transcription of galactose  metabolizing proteins by not allowing Gal4 to bind to/attract co-activators Gal 3 - allosteric protein that, when bound to galactose, changes conformation and binds to  Gal80, which cancels binding of Gal80 to Gal4, and allows Gal4 to attract/bind to co-activators Use of Gal4 in transgeneic flies  - since Gal4 receptor domain can be switched to various  DNA binding domains and still used as a transcription activator, we can insert Gal4 into flies  that previously did not have galactose used as a regulatory effector and control transcription of  targeted genes. Mediator Complex  - a co-activator in Gal regulation in yeast - when Gal4 is free of Gal80, the  mediator complex binds to Gal4, and also recruits RNA Poly II to being transcription of  galactose metabolizing proteins TFIID  - transcription factor that binds to the TATA binding factor and attaches to Gal4 when it  is free of Gal80. The binding of this and the mediator complex to Gal4 folds the DNA to bring 
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the entire system closer to the promoter, hence bringing RNA Poly II closer to the promoter as  well.  Bacterial DNA vs. Eukaryotic DNA  - bacterial DNA 'naked' and not packed, transcription can  happen anywhere along the DNA, whilst eukaryotic DNA is organized into packed  heterochromatin (methylated histone tails) where transcription cannot occur, and euchromatin  (acetylated histone tails) where transcription CAN occur.
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