BBMB 405 1st Edition Lecture 30 Outline of Last Lecture XV Chapter 29 RNA synthesis and Processing B RNA polymerases catalyze transcription con t C Transcription in eukaryotes is highly regulated Outline of Current Lecture XV Chapter 29 RNA synthesis and Processing C Transcription in eukaryotes is highly regulated con t Current Lecture XV Chapter 29 RNA synthesis and Processing C Transcription in eukaryotes is highly regulated con t 1 Riboswitches can flip on a Turn on gene and can control genes that are involved in degredation or removal of metabolite b Moved out where concentration of adenine is low then released from complex and create terminator c Orphanriboswitches predicted structure in 5 area but don t know purpose ligand in front of genes none of predicted ligands bind d Orthogonal riboswitches researchers take naturally occurring and do in vitro evolution experiment create riboswitch that can bind to molecule not found in natural cell 2 TATA box versus CpG island promoters 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 a Defined transcription start site within Initiator sequence b TATA box is recognized by TBP without additional factors c Found in tissue specific promoters d Can have multiple transcription start sites leading to mRNAs with different 5 UTRs e TATA box is binding by TBP is assisted by additional transcription factors f Found in promoters for housekeeping genes 3 Formation of preinitiation complex by general transcription factors a Transcription factor IID TFIID TBP and 16 TBP associated factors TAFs bind the TATA box b TFIIB important for start site selection c TFIIE facilitates DNA unwinding d TFIIH Complex of 10 subunits including helicases involved in DNA unwinding and kinases involved in Pol II C terminal phosphorylation e 4 Many RNAs are processed post transcriptionally 5 Polycistronic pre rRNAs transcripts must be cleaved a Cleavage is dependent on the U3 small nucleolar RNA snoRNA bind and present functional region containing 2 5 MDa small subunit SSU essential in forming ribosome processome b Cistron gene polycistron multiple genes polycistronic transcript multiple genes within a single transcript c Pre RNA is folded and assembled in nucleolus very dense granule localized as sight for RNA construction not bound by membrane d Why RNA used to make RNA RNA really big ensures right cleavage site 6 Modification a Involves snoRNA b Types methylation of nucleobase or ribose c Important in structure and stability d e f Effects on structure above 7 Transfer RNA processing a Leader sequence cleaved off so can be function cleaved by RNase P multiturnover enzyme release product and catalyze reaction recycle self b Triming of 3 end and addition added by CCA enzyme attach amino acid to site c May contain introns that have to be spliced out splicing by endonuclease kinase and RNA ligase eukaryotes and archaea or through self splicing bacteria 8 RNase P is a multi turnover ribozyme 9 Eukaryotic pre mRNA processing a Tag at 5 end Bacteria keeps triphosphate eukaryote gets modified Begin with triphosphate first step is gamma phosphate is removed RNA triphosphatase Add GTP via mRNA guanylyltransferase Use SAM to methylate G via guanylyl N7 methyltransferase Protection resembles 3 end instead because have a base rather than a phosphate Important in recognition b 3 end 3 polyadenylation Stabilizes mRNA and enhances translation Protects through binding of poly A binding protein which coats end Acts as signal for recruitment of transcription factors Can introduce isoforms
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