CMB 311 Lecture Notes - Lecture 16: Phosphodiester Bond, Transcription Factor Ii H, Spooling
26 Jan 2019
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Eukaryotic RNA Synthesis, modification, processing, splicing 11/28
● tRNA and rRNA precursors are modified and processed to produce the mature,
functional form (of all organism)
● mRNA are modified before translation (Eukaryotes)
● Unknown why we have introns, good question
● Polymerases
○ RNA Pol I, II, and III
○ Focusing on RNA Pol II; to synthesize mRNA
● RNA Pol II
○ Synthesis of mRNA
○ 12 subunits
○ CTD (C-terminal domain) very important
■ 52 copies of sequence , not well structured ( there but cant see)
■ Other proteins bind to it that involved in processing and modifying the
RNA
○ Initiation
■ Alot of proteins come in during this step then leave
● Phosphodiester bond formation
● CTD phosphorylating by TFIIH
○ 5’ Cap
■ ENzymes come and add a linkage, attached to 5’ end of the message.
Normally its 5’ to 3’ in same direction, in this case it's 5’ to 5’
■ Roll of cap is prevent degradation of ribonucleases
■ Important for regulation
■ During transcription the 5’ end is tethered to the CTD of RNA Pol II
● As RNA is being made, spooling out but still connected to CTD
● CBD ( cap-binding complex)
○ 3’ end Polyadenylated
■ Prevents degradation by exoribonucleases
■ Poly A tail is not coded, not sequenced in DNA
● Length varies from one molecule to another
○ Eukaryotic mRNAs contain introns removed by splicing
■ Intros not part of the coding sequence
■ Nobody knows why we have introns
■ Mature mRNA is exported to the cytoplasm
○ rRNA and tRNA processing; cutting and trimming
■ Functional molecules
■ rRNA makes up bulk of ribosome
■ tRNA brings amino acid to ribosome
■ Both come and trim away to result in final product
● Large number of enzymes involved in the processes
●
● Ribonuclease P
Document Summary
11/28 trna and rrna precursors are modified and processed to produce the mature, functional form (of all organism) Unknown why we have introns, good question. Focusing on rna pol ii; to synthesize mrna. 52 copies of sequence , not well structured ( there but cant see) Other proteins bind to it that involved in processing and modifying the. Alot of proteins come in during this step then leave. Enzymes come and add a linkage, attached to 5" end of the message. Normally its 5" to 3" in same direction, in this case it"s 5" to 5". Roll of cap is prevent degradation of ribonucleases. During transcription the 5" end is tethered to the ctd of rna pol ii. As rna is being made, spooling out but still connected to ctd. Poly a tail is not coded, not sequenced in dna. Length varies from one molecule to another. Eukaryotic mrnas contain introns removed by splicing.
