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28 Cards in this Set
- Front
- Back
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What are the requirements of RNA transcription?
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1. template
2. rNTP's 3. Proteins |
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What are some keys about RNA polymerase?
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adds rNTP's, releases pyrophosphate to make phophodiester bond, does not need a primer to start transcription, starts at +1 site
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describe the promoter:
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minimal sequence needed for RNA polymerase to bind
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What happens in the transcription process?
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1. polymerase binds to promoter in duplex DNA "closed complex"
2. polymerase melts duplex DNA near transcription start site, forming a transcription bubble "open copmlex 3. polymerase catalyzes phosphodiester linkage of two initial rNTPs 4. polymerase advances down template strand, melting dupluex dna, andding rNTPs 5. termination- at transcription stop site, polymerase releases and RNA dissociates |
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how is prokaryotic transcription carried out?
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genes are usually in operons, and are one after another, 1 mRNA is translated into multiple proteins
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how is eukaryotic transcription carried out?
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genes are separate, with separate promoters, separate transcription and intron splits
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what are sigma factors? what do these shits do?
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proteins that bind to RNA polymerase, they recognize specific sequences in the gene and recruit polymerase.
also is part of the rna polymerase complex unwinds the DNA comes in the iniation step, then dissociates to other RNA |
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What are the parts of the lac operon?
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CAP site, promoter, +1, operator, lacz
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describe the CAP
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activated by cAMP. helps polymerase bind to DNA
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what is the lac repressor?
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binds to the operator (weakly)
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What characterizes condensed chromatin?
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methylation, methylation of lys 9, hp1 is the only protein that can promote the closed state, binds to methyl modification with chromodomain, can oligomerize with other hp1s, bring in more methyl transferase
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how to unwind condensed chromatin?
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activators: proteins that bind to DNA and recruit other proteins
demethylases, acetylases repressors are opposite |
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what is the carboxyl-terminal domain?
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7 amino acid repeats, SYT can be phosphorylated
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What are promoter proximal elements?
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upstream, close to +1 site
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What are enhancers?
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located far from +1 site
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What types of general promoter elements are there?
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TATA box, initiator, CPG island
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Describe the TATA box:
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position the RNA polymerase, located about 25 - 30 upstream, TBP
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Describe Initiators
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-1 and -2 should be pyrimidines?
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Describe the CPG island
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20-50 upstream of start site, Cs and Gs, not as specific as tata box
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Describe a modular protein
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different domain with different fuctions
have 1. dna binding domain 2. activator domain to up/downregulator3. flexible protein domain |
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Describe a homodimer
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two identical proteins bound to a site, happens when there is repeats in sequence
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Describe a heterodimer
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when two different proteins bind close,
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What happens cooperative dna binding?
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in two sites, each protein cannot bind, but it is allowed when proteins interact with other proteins
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What's a mediator?
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multiprotein complex that bridges activators to RNA pol II and general transcription factors
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How is the pre-initiation complex formed?
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1. activators bind DNA sequence (enhancer)
2. activator recruits cofactors to loosen dna interactions 3. activator recruits acetylases 4. other activators like proximal are introduced 5. activators recruit mediator 6. mediator recruits pol II and general transcription factors |
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What do nuclear receptors do?
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o 1. Bind hormone (ligand – something that binds that changes the activity)
o 2. Activate (usually) transcription o 3. Dimeric, either homodimers or heterodimers, all homodimers bind on separate strands, heterodimers bind on the same strand o homodimeric nuclear receptors have to have the ligand in order to activate. They stay cytoplasmic unless the ligand is present then will go into nuclear membrane |
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What characterizes homodimer nuclear receptors?
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Nuclear receptors (type of transcription factors)
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What characterizes heterodimeric nuclear receptors?
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o 1. Nuclear
o 2. Bind dna repress transription in absence of ligand activate transcription upon binding ligand first nuclear receptor is RXR usually. Receptors are ALWAYS bound to the DNA |
