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Lecture 22

BIO 1140 Lecture Notes - Lecture 22: Small Interfering Rna, Rna Interference, Microrna


Department
Biology
Course Code
BIO 1140
Professor
Doug Johnson
Lecture
22

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Cell Bio Lecture 22
Regulation of Gene Expression in Eukaryotes Occurs at Many Levels
Organization of a “Eukaryotic Gene”
Eukaryotic gene organization allows regulation
- Promoter includes TATA box that binds transcription factors
- Promoter proximal region upstream of promoter increases transcription
- Enhancer further determines maximum transcription rate (what are silencers)
- Regulation involves integrating different circuits that say whether to increase or
decrease
- You can have regulatory sequences that are away from the promoter, distal
element (so we have proximal and distal elements)
- Darkened sequences refer to cis-acting sequences and they bind trans-acting
proteins.
- If they increase expression and they are close, proximal, they are not called
enhancers. If they increase it and they are distal they are called silencers
- All the sequences have the bases of increasing or decreasing production and
binding proteins to DNA
Transcription Complex form on Promoters
How do these factors assemble to initiate transcription?
- Bind to TATA box area and recruit RNA polymerase II
- Transcriptional initiation complex, low rate (basal)
- Activators bind to promoter proximal elements and increase transcription rate
- Repressors do what?
Slide 19
Chromatin Amino precipitation techniques
Regulation of Transcription Initiation
- Coactivators bidge enhancer and promoter. – Interactions between coactivator,
proteins at promoter, and RNA polymerase increase transcription
- Repressors oppose effect of activators. – Trancription rate depends on activation
and repression signals. In a multicellular organism these signals may be external
(heat, light etc.) or internal (hormones etc). May bind to sites on an activator or
coactivator or increase association with histones.
Overall regulation is a balance of many factors
Combinatorial gene regulation: a simple model
- A signal says to activate or repress a circuit, which will cause activators or
repressors to bind to the enhancer regulatory sequences
- There will often be multiple genes being activated or repressed by different
activators or repressors
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