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SC BIOL 302 - Termination vs Transcription

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BIOL 302 1nd Edition Lecture 14Outline of Current LectureI. TranscriptionII. Terminationa. Prokaryotic Terminationb. Eukaryotic TerminationCurrent LectureI. Transcription a. You can’t get DNA because limited access to nucleosomes and chromatin (represses transcription)b. SWI/SWF: have enzymatic activities that modify to allow recognition by other factions and access to DNA sequencesc. Histone acetyl-transferase (HAT): where the acetyl group adds ond. Histone de-acetyl-transferse (HDA): where the acetyl group detaches i. When the C terminal ----- NH terminal: with all positive charges to interactwith the negative at neutral pH ~ + chargeii. The acetyl group makes it negatively charge due to the histones losing their grip on the DNA (genes are on)iii. HD (inactive ---- HAT (active)1. Promotes specific interactions with tafs – ex: (SP1 with taf 250): when the transcription is building up it brings the taf250 in the DNA complex and acts as the recruiter to the taf250 and starts to undo the chromatin2. Which happens on different histones at different times e. H3 (super complicated)i. All modifications can happen in different paths with different combinations – the Histone Code: that code signals when genes are goingto turn on or off and carry out some kind of actions.ii. 30 nm fiber – somewhere there has to be a gene that turns on which acts as a substrate (pioneer factor) and starts to come apart and remodels the chromatin (beads on a string). These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.1. How do they know where they are located? Modification on the genes to expose where they are. Histones have some kind of modification. 2. Bre1: factor that locates where the gene is 3. Pioneer: replaces Histones H1 and starts to come apart (ex. A1)II. Terminationa. Bacteria has a termination signal and eukaryotes don’t i. E.Coli can end the process with a termination signal which is in the DNA transmitted by RNA – when in the RNA it is active and binds to NUSA: inhibits the polymerase from transcribing until it reaches the last U in the sequence.ii. 2 is required for termination:1. has to be GC rich in the stem loop within 8 nucleotides because it makes it more stable2. all the U’s in the sequence have to be at the end (unstable) in order for it to stop. This helps it recognize the structure. b. Eukaryotic Terminationi. There isn’t really any termination going on. ii. Sequence is required and presence in eukaryotic cells. mRNA at the 10-20point 3’ end (polyadenylation signals a reaction that cuts the 3’ end but keeps the polymerase going on, the RNA falls off.iii. Primary transcript: has to be modified in 3 ways: at the 5’ cap, at AAA, and splicing1. Splicing: the introns need to be removed because the exons are needed to be together2. 5’ cap: happens in every message (mRNA) soon after initiation but before termination 3. A/G: are the start sites in most genes while 5’ end has the triphosphate and guanine (with an extra methyl group) is added on the 5-carbon to 5’ end4. Adds AAA in the 3’ end (polyA tail) only one that doesn’t require a


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SC BIOL 302 - Termination vs Transcription

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