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23 Cards in this Set
- Front
- Back
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What are the steps of eukaryotic RNA Initiation?
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1. Rearrangement of chromatin.
2. Binding of transcription factors. 3. Binding of the RNA polymerase to the promoter. |
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Eukaryotic Initiation
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-chemical modification of bases of DNA and histones (methylation)
-acetylation of histones |
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acetylation of histones
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-catalyzed by HAT
ie: lysine acetylation - removes the positive charge --- reduce the interaction between histones and (-) charged DNA -------- allow polymerase to have access to DNA |
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deacetylation of histones
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-catalyzed by HDAC
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What is a Promoter?
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A DNA segment containing specific sequencing for binding of transcriptio nfactors and RNA polymerase
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cis-acting element
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transcription factor that is covalently linked to the gene
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trans-acting element
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transcription factor non-covalently linked to the gene
RNA polymerase transcription factors are trans-acting |
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General vs. Specific Transcription factors
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General-
Specific- |
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Specific Transcription Factor Roles
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modulate efficiency of initiation
mediate signal response regulates gene expression (locate in specific tissues turn on specific class of genes) bind to other regulatory proteins (co-activators) |
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Elongation Requirements
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RNA polymerases
all 4 NTPs |
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Termination Requirements
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termination sequence (cis-acting)
protein factors |
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Key Points on eukaryotic tRNA
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1. INTERNAL PROMOTER: binding sites for transcription factors and RNA poly III
2. Transcription products (RNA) contain promoter sequence |
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methylation of DNA
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cis-acting reaction, means of modification
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Post-transcriptional modifications of tRNA
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1. addition of CCA at the 3' ent of the tRNA
w/o it will not be funtional 2. bases and sugars methylation, dihydro-U |
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2 pathways of rRNA synthesis
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RNA pol I-
RNA pol III |
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gene for mRNA
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ENHANCER - PROMOTER - transcribed region (interone, exons, poly A site, termination site)
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CAAT box
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component of mRNA promoter
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TATA box
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portion of promoter after te CAAT box and the GC-rich regions
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Important Properties of Enhancers
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1.
2. 3. 4. |
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RNA Pol I
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5.8S, 18S, and 28S rRNA
nucleolous insensitive to both alpha-amanitin and rifampicin |
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RNA Pol II
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mRNA, snRNA
nucleoplasm strongly inhibited by alph-amanitin insensitive to rifampicin |
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RNA Pol III
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tRNA, 5S rRNA
nucleoplasm inhibited by high concentrations by alpha-amanitin insensitive to rifampicin |
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Mitochondrial RNA Pol
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mito RNAs
mitochondria insensitive to alpha-amanitin inhibited by rifampici |
