341lecture09sept28sakai

341lecture09sept28sakai - Cell Biology 341 Monday Sept 28...

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Cell Biology 341 Monday, Sept. 28, 2009 Today: Initiation of transcription in eucaryotic cells 3 steps in processing of primary transcripts in eucaryotic cells Go to http://firstglance.jmol.o to use PDB codes shown on your slides (a single core nucleosome is PDB code1eqz) Last lecture: finished chapter 4 Gene activation requires chromatin remodeling and/or partial removal, replacement or modification of core histones Began Chapter 6: Transcription and translation are coupled in procaryotic cells, but occur in separate compartments in eucaryotic cells RNA polymerase transcribes DNA into RNA, adding nucleotides to the 3′-OH of the RNA molecule Procaryotic RNA pol requires sigma factor for tight binding to the promoter (-10) and (-35) sequences
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Regulation of transcription in eucaryotic cells There are three nuclear RNA polymerases in eucaryotic cells They resemble each other and the procaryotic RNA pol in structure, but have many more subunits (RNA pol II = 12 subunits = 587,000 Daltons in yeast; procaryotic = 4 subunits + σ = 460,000 Da) Mitochondria and chloroplasts also have their own RNA polymerases The three nuclear forms of RNA pol transcribe genes with different types of promoters RNA pol I transcribes most rRNA genes (5.8S, 18S and 28S) in the nucleolus RNA pol II transcribes all protein-coding genes, most snRNAs and some other small RNAs RNA pol III transcribes all tRNA genes, the 5S rRNA gene and some small RNAs
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All nuclear RNA polymerases require other
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