Lect19.RNA.part2

Lect19.RNA.part2 - LECTURE 19: RNA REGULATORY MECHANISMS...

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LECTURE 19: RNA REGULATORY MECHANISMS Levels of specific messenger RNAs can differ in different types of cells and at different times in the same cell. In prokaryotes, control of RNA abundance can be at the level of transcription initiation or transcription elongation (attenuation). In eukaryotes, RNA abundance is regulated by transcription initiation, attenuation, splicing, or rate of RNA degradation. Control of transcription initiation in eukaryotes is exerted in gene-specific manner by sequence-specific DNA binding proteins and in a region- or chromosome-wide manner by covalent modifications of DNA or chromatin.
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Sequence Specific Homodimeric DNA Binding Proteins Bind DNA Palindromes Protein sides chains often achieve binding specificity by hydrogen bonding with base motifs within the DNA major groove.
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BLZ Factors are Another Class of Homomeric DNA Binding Proteins
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Homeodomain-Containing Factors Contain Helix-Turn-Helix Motif Heterodimerization provides greater target specificity by lengthening recognition sequence.
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Multiple Zinc Fingers Allow Complex Sequence Recognition
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Prokaryotic Regulation by Induction and Repression of Transcription Initiation Lactose catabolism utilizes regulation at the LAC operon
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Lac Operon Encodes Multiple Proteins Involved in Lactose Metabolism Lac repressor is constitutively synthesized from the LacI gene Repressor binds to operator (LacO) just downstream of operator promotor and prevents operon transcription by blocking RNA polymerase movement Lactose or non-hydrolizable analogs bind the repressor and prevent its binding to LacO, thereby promoting operon transcription
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Glucose Inhibits Lac Operon Transcription Initiation by Catabolite Repression Efficient binding of RNA polymerase to the
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Lect19.RNA.part2 - LECTURE 19: RNA REGULATORY MECHANISMS...

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