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21 Cards in this Set
- Front
- Back
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What is the TATA box?
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~25 nucleotides upstream from promoter
- directs RNA polymerase to transcription site |
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What is the CAAT box?
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~75 nucleotides upstream from promotor
- helps recruit RNA polymerase |
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What is the purpose of transcription factors?
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- help regulate efficiency of TATA and transcription site
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What is a promotor?
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- DNA sequence that specifies position and direction of RNA polymerase initiation
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What is an enhancer?
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- DNA sequence that stimulates RNA polymerase II transcription (binding site for proteins)
- it is position and orientation independent |
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RNA polymerase I transcribes.
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rRNAs (28S, 18S, 5.8S)
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RNA polymerase II transcribes
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mRNA, microRNA
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RNA polymerase III transcribes
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small RNA (tRNA, 5sRNA)
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What are the regions on DNA called that are able to be attacked by nucleases?
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- hypersensitive sites
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What are the 2 examples discussed of ways to regulate transcription?
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1) heat-shock gene transcription
2) steroid regulated gene activation |
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Describe the transcription regulation by heat shock genes
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-Heat shock factor (HSF) is a monomer in normal conditions
- RNA polymerase already bound to promoter and has transcribed a few nucleotides, then paused - heat/stress leads to trimerization of HSF - trimer binds to target areas on DNA - HSF binding increases transcription |
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Describe the transcription regulation by steroid hormone activation
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- hormone diffuses through cell membrane
- hormone displaces inhibitory protein complex from steroid hormone receptor - complex passes into nucleus - dimerizes and binds to target sequence on DNA - may activate/inhibit transcription - if activates: recruits RNA polymerase for transcription |
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LCR and human globin genes
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- Locus control region is a 40,000 nucleotide sequence upstream of the normal human globin locuses that contains enhancers required for transcription of globin
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Hispanic deletion
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- LCR is deleted, therefore there is no expression of the globin genes
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What are the 3 post-translation modifications of mRNA and their purposes
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1) 5' cap (ribosome recognizes mRNA)
2) 3' poly-A tail (stability of mRNA from ribonucleases degrading) 3) splicing (removes introns, keeps exons) |
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What creates the lariate intron structure?
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- the 2' OH of the A on the branch site attacks the final G on the intron (between intron 1 and exon 1), creating a loop
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What is the purpose of alternative splicing?
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- yields multiple isoforms
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What are miRNAs?
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- areas between the 3' UTR and poly-A tail that are transcribed, but do not encode proteins
- they are chopped up by DICER into 21-23 nucleotide fragments |
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What do miRNAs do?
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- down-regulate gene expression
- contain complementary base pairs to mRNA - base pair is complete targets mRNA for degradation - base pair incomplete leads to inefficient translation of mRNA |
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How do viruses exploit miRNAs?
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- contain Viral pri-miRNA
- miRNA processed by host cell - Host Risc picks up viral mRNA - viral miRNA targets host viral response mRNA and inhibits them |
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How does Dicer create miRNA?
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- mRNA that folds back on itself is the target
- Dicer cleaves it into 21-23 nucleotide pieces - miRNA target for protein complex, Risc - Risc recognizes dsRNA and strips 1 strand off - ssRNA is able to pair with target mRNA |
