lec.5-7.euk_trxn_apparatus

lec.5-7.euk_trxn_apparatus - Three types of RNA polymerase...

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Three types of RNA polymerase in eukaryotic nuclei Type Location RNA synthesized Effect of α -amanitin I Nucleolus Pre-rRNA for 18, 5.8 and 28S rRNAs Insensitive II Nucleoplasm Pre-mRNA, some snRNAs Sensitive to 1 μ g/ml III Nucleoplasm Pre-tRNAs, 5S rRNA, some snRNAs Sensitive to 10 μ g/ml (Also- Organelle RNAPs in Mitochondria and Chloroplasts. Encoded by organelle genomes. Similar to bacterial RNAPs.) α -amanitin from Amanita Phalloides binds tightly to RNA Pol II and blocks transcriptional elongation. RNA Pol I transcribe 1 gene at ~200 copies. The gene for the 45S pre-rRNA is present in tandem array. RNA Pol II transcribe ~25,000 genes; RNA Pol III transcribe 30-50 genes at variable copy numbers.
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Subunit composition of  eukaryotic RNA polymerases •All three yeast polymerases have five core  subunits that exhibit some homology with the  β β ‘,  α  and  ϖ  subunits in  E. coli  RNA  polymerase.  •RNA polymerases I and III contain the same  two non-identical  α -like subunits, whereas  polymerase II has two copies of a different  α - like subunit. •All three polymerases share four other  common subunits. In addition, each RNA  polymerase contains three to seven unique  smaller subunits. •The largest subunit (1) of RNA polymerase II  also contains an essential C-terminal domain  (CTD). 27 (yeast) to 52 (human) copies of  (YSPTSPS).  •Phosphorylation of CTD is important for  transcription and RNA processing.
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Comparison of 3-D structures of bacterial and eukaryotic RNA polymerases (subunits 4 and 7 are missing)
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Cyan: alternating β -turns; Pink: extended regions.
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This note was uploaded on 03/08/2010 for the course MCB 110 taught by Professor Alber,zhou,nogales during the Fall '07 term at University of California, Berkeley.

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lec.5-7.euk_trxn_apparatus - Three types of RNA polymerase...

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