1. CS173 Lecture 9: Transcriptional regulation III
MW  11:00-12:15 in Beckman B302
Prof: Gill Bejerano
TAs: Jim Notwell & Harendra Guturu
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2. Announcements Halfway feedback end of class today
Undergrads: CURIS in summer
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3. TTATATTGAATTTTCAAAAATTCTTACTTTTTTTTTGGATGGACGCAAAGAAGTTTAATAATCATATTACATGGCATTACCACCATATACATATCCATATCTAATCTTACTTATATGTTGTGGAAATGTAAAGAGCCCCATTATCTTAGCCTAAAAAAACCTTCTCTTTGGAACTTTCAGTAATACGCTTAACTGCTCATTGCTATATTGAAGTACGGATTAGAAGCCGCCGAGCGGGCGACAGCCCTCCGACGGAAGACTCTCCTCCGTGCGTCCTCGTCTTCACCGGTCGCGTTCCTGAAACGCAGATGTGCCTCGCGCCGCACTGCTCCGAACAATAAAGATTCTACAATACTAGCTTTTATGGTTATGAAGAGGAAAAATTGGCAGTAACCTGGCCCCACAAACCTTCAAATTAACGAATCAAATTAACAACCATAGGATGATAATGCGATTAGTTTTTTAGCCTTATTTCTGGGGTAATTAATCAGCGAAGCGATGATTTTTGATCTATTAACAGATATATAAATGGAAAAGCTGCATAACCACTTTAACTAATACTTTCAACATTTTCAGTTTGTATTACTTCTTATTCAAATGTCATAAAAGTATCAACAAAAAATTGTTAATATACCTCTATACTTTAACGTCAAGGAGAAAAAACTATAATGACTAAATCTCATTCAGAAGAAGTGATTGTACCTGAGTTCAATTCTAGCGCAAAGGAATTACCAAGACCATTGGCCGAAAAGTGCCCGAGCATAATTAAGAAATTTATAAGCGCTTATGATGCTAAACCGGATTTTGTTGCTAGATCGCCTGGTAGAGTCAATCTAATTGGTGAACATATTGATTATTGTGACTTCTCGGTTTTACCTTTAGCTATTGATTTTGATATGCTTTGCGCCGTCAAAGTTTTGAACGATGAGATTTCAAGTCTTAAAGCTATATCAGAGGGCTAAGCATGTGTATTCTGAATCTTTAAGAGTCTTGAAGGCTGTGAAATTAATGACTACAGCGAGCTTTACTGCCGACGAAGACTTTTTCAAGCAATTTGGTGCCTTGATGAACGAGTCTCAAGCTTCTTGCGATAAACTTTACGAATGTTCTTGTCCAGAGATTGACAAAATTTGTTCCATTGCTTTGTCAAATGGATCATATGGTTCCCGTTTGACCGGAGCTGGCTGGGGTGGTTGTACTGTTCACTTGGTTCCAGGGGGCCCAAATGGCAACATAGAAAAGGTAAAAGAAGCCCTTGCCAATGAGTTCTACAAGGTCAAGTACCCTAAGATCACTGATGCTGAGCTAGAAAATGCTATCATCGTCTCTAAACCAGCATTGGGCAGCTGTCTATATGAATTAGTCAAGTATACTTCTTTTTTTTACTTTGTTCAGAACAACTTCTCATTTTTTTCTACTCATAACTTTAGCATCACAAAATACGCAATAATAACGAGTAGTAACACTTTTATAGTTCATACATGCTTCAACTACTTAATAAATGATTGTATGATAATGTTTTCAATGTAAGAGATTTCGATTATCCACAAACTTTAAAACACAGGGACAAAATTCTTGATATGCTTTCAACCGCTGCGTTTTGGATACCTATTCTTGACATGATATGACTACCATTTTGTTATTGTACGTGGGGCAGTTGACGTCTTATCATATGTCAAAGTTGCGAAGTTCTTGGCAAGTTGCCAACTGACGAGATGCAGTAACACTTTTATAGTTCATACATGCTTCAACTACTTAATAAATGATTGTATGATAATGTTTTCAATGTAAGAGATTTCGATTATCCACAAACTTTAAAACACAGGGACAAAATTCTTGATATGCTTTCAACCGCTGCGTTTTGGATACCTATTCTTGACATGATATGACTACCATTTTGTTATTGTACGTGGGGCAGTTGACGTCTTATCATATGTCAAAGTCATTTGCGAAGTTCTTGGCAAGTTGCCAACTGACGAGATGCAGTTTCCTACGCATAATAAGAATAGGAGGGAATATCAAGCCAGACAATCTATCATTACATTTAAGCGGCTCTTCAAAAAGATTGAACTCTCGCCAACTTATGGAATCTTCCAATGAGACCTTTGCGCCAAATAATGTGGATTTGGAAAAAGAGTATAAGTCATCTCAGAGTAATATAACTACCGAAGTTTATGAGGCATCGAGCTTTGAAGAAAAAGTAAGCTCAGAAAAACCTCAATACAGCTCATTCTGGAAGAAAATCTATTATGAATATGTGGTCGTTGACAAATCAATCTTGGGTGTTTCTATTCTGGATTCATTTATGTACAACCAGGACTTGAAGCCCGTCGAAAAAGAAAGGCGGGTTTGGTCCTGGTACAATTATTGTTACTTCTGGCTTGCTGAATGTTTCAATATCAACACTTGGCAAATTGCAGCTACAGGTCTACAACTGGGTCTAAATTGGTGGCAGTGTTGGATAACAATTTGGATTGGGTACGGTTTCGTTGGTGCTTTTGTTGTTTTGGCCTCTAGAGTTGGATCTGCTTATCATTTGTCATTCCCTATATCATCTAGAGCATCATTCGGTATTTTCTTCTCTTTATGGCCCGTTATTAACAGAGTCGTCATGGCCATCGTTTGGTATAGTGTCCAAGCTTATATTGCGGCAACTCCCGTATCATTAATGCTGAAATCTATCTTTGGAAAAGATTTACAATGATTGTACGTGGGGCAGTTGACGTCTTATCATATGTCAAAGTCATTTGCGAAGTTCTTGGCAAGTTGCCAACTGACGAGATGCAGTAACACTTTTATAGTTCATACATGCTTCAACTACTTAATAAATGATTGTATGATAATGTTTTCAATGTAAGAGATTTCGATTATCCACAAACTTTAAAACACAGGGACAAAATTCTTGATATGCTTTCAACCGCTGCGTTTTGGATACCTATTCTTGACATGATATGACTACCATTTTGTTATTGTTTATAGTTCATACATGCTTCAACTACTTAATAAATGATTGTATGATAATGTTTTCAATGTAAGAGATTTCGATTATCCTTATAGTTCATACATGCTTCAACTACTTAATAAATGATTGTATGATAATGTTTTCAATGTAAGAGATTTCGATTATCCTTATAGTTCATACATGCTTCAACTACTTAATAAATGATTGTATGATAATGTTTTCAATGTAAGAGATTTCGATTATCCTTATAGTTCATACATGCTTCAACTACTTAATAAATGATTGTATGATAATGTTTTCAATGTAAGAGATTTCGATTATCCTTATAGTTCATACATGCTTCAACTACTTAATAAATGATTGTATGATAATGTTTTCAATGTAAGAGATTTCGATTATCCTTATAGTTCATACATGCTTCAACTACTTAATAAATGATTGTATGATAATGTTTTCAATGTAAGAGATTTCGATTATCCTTATAGTTCATACATGCTTCAACTACTTAATAAATGATTGTATGATAATGTTTTCAATGTAAGAGATTTCGATTATCCTTATAGTTCATACATGCTTCAACTACTTAATAAATGATTGTATGATAATGTTTTCAATGTAAGAGATTTCGATTATCTTATAGTTCATACATGCTTCAACTACTTAATAAATGATTGTATGATAATAAAG
Genome Content
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4. Transcription Regulation
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5. Gene Regulation
Some proteins and non coding RNAs go “back” to bind DNA near genes, turning these genes on and off.
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6. Transcription Activation
Terminology:
RNA polymerase
Transcription Factor
Transcription Factor Binding Site
Promoter
Enhancer
Gene Regulatory Domain TF
DNA
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7. Transcriptional Repression
Transcription factors can bind key genomic sites, preventing/repelling the binding of
The RNA polymerase machinery
Activating transcription factors
DNA can be bent into 3D shape preventing enhancer – promoter interactions.
Activator and co-activator proteins can be modified into inactive states.
Activation and repression counter-act to provide the cell the needed levels of output from the same stretch of DNA under the many cellular conditions all served by (identical copies of) the same genome.
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8. Locus Control Region
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9. Nucleosomes, Histones, Transcription
Chromatin / Proteins
Genome packaging provides a critical layer of gene regulation.
DNA / Proteins
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10. Chromosome Centromere
region of DNA typically found near the middle of a chromosome where two identical sister chromatids come in contact. It is involved in cell division
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11. Heterochromatin & Euchromatin
Tightly coiled chromosome material; believed to be mostly genetically inactive.
Euchromatin:
Where temporal opening and closing of chromatin (“nucleosome positioning”) and transcription takes place.
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12. Insulators
Insulators are DNA sequences that when placed between target gene and enhancer prevent enhancer from acting on the gene.
Known insulators contain binding sites for a specific DNA binding protein (CTCF) that is involved in DNA 3D conformation.
However, CTCF fulfills additional roles besides insulation. I.e, the presence of a CTCF site does not ensure that a genomic region acts as an insulator.
TSS1
TSS2
Insulator
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13. Signal Transduction
Everything we discussed so far happens within the cell. But cells talk to each other, copiously.
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14. Enhancers as Integrators
IF the cell is part of a certain tissue AND receives a certain signal
THEN turn Gene ON
Gene
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15. Gene Regulation Chromatin / Proteins Extracellular signals
DNA / Proteins
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16. Histone Tails, Histone Marks
DNA is wrapped around nucleosomes.
Nucleosomes are made of histones.
Histones have free tails.
Residues in the tails are modified in specific patterns in conjunction with specific gene regulation activity.
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17. Histone Mark Correlation Examples
Active gene promoters are marked by H3K4me3 Silenced gene promoters are marked by H3K27me3 p300, a protein component of many active enhancers acetylates H3k27Ac.
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18. Measuring these different states
Note that the DNA itself doesn’t change. We sequence different portions of it that are currently in different states (bound by a TF, wrapped around a nucleosome etc.)
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19. Epigenomics: study all these marks genomewide
Translate observations into current genome state.
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20. Obtain a network of all active genes & DNA
Now what? (to be revisited)
“Ridicilogram”
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21. Histone Code Hypothesis
Histone modifications serve to recruit other proteins by specific recognition of the modified histone via protein domains specialized for such purposes, rather than through simply stabilizing or destabilizing the interaction between histone and the underlying DNA.
histone modification:
writer
eraser …
reader
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22. Cis-Regulatory Components
Low level (“atoms”):
Promoter motifs (TATA box, etc)
Transcription factor binding sites (TFBS)
Mid Level:
Promoter
Enhancers
Repressors/silencers
Insulators/boundary elements
Locus control regions
High Level:
Epigenomic domains / signatures
Gene expression domains
Gene regulatory networks
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23. Epigenomics is not Epigenetics
Epigenetics is the study of heritable changes in gene expression or cellular phenotype, caused by mechanisms other than changes in the underlying DNA sequence There are objections to the use of the term epigenetic to describe chemical modification of histone, since it remains unknown whether or not these modifications are heritable.
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24. Almost done with genome content & function
We’ve talked about transcripts and their regulation. We’re still ignore at least half the genome…
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25. To be continued
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26. Halfway Feedback Thank you!
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