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Lecture 6

CBIO 3400 Lecture Notes - Lecture 6: Transferase, Eukaryotic Translation, 3D Cell Culture


Department
Cellular Biology
Course Code
CBIO 3400
Professor
Shen
Lecture
6

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CBIO 3400
Exam 4 Lecture 6B- New Lecture Material
04/05/2019
mRNA Processing (Splicing Focus)
mRNA stability:
We don’t want it immediately degraded.
o So we can translate it, get products from it.
We also don’t want it to hang around forever.
o Want it to be degraded at some point. don’t want to make certain genes all the
time and waste energy
We want to precisely control how much and for how long.
o Want to control how much RNA is around and for how long
RNA Pol II CTD: A Very Long Tail That Binds Pre-mRNA Processing Factors
Enzymes involved in 5' capping, polyadenylation, and splicing bind to the long
phosphorylated CTD of RNA Pol II
Tail is used in lots of ways as a loading platform
Regulation Starts Before the Message Is Completed
RNA processing enzymes associate with phosphorylated CTD tail of RNA Pol II (Loaded
on in stages, some in initiation, elongation, and termination)
o Capping Factors
o Splicing Factors
o 3’ End Processing Proteins
What is the 5’ 7-Methyl-G Cap?
Added after the nascent RNA molecules reach a length of 25-30 nucleotides.
Guanylyltransferase binds to the Ser5-phosphorylated Pol II CTD and adds GTP.
As serine 5 is phosphorylated, this serves as a platform for guanyl transferase to
add GTP to nascent mRNA.
The methyl groups are derived from S-adenosylmethionine.
**5’ 7-Methyl-G Cap is a GTP that’s been added from its 5’ carbon to 5’ carbon on nascent
mRNA. Strange 5’ to 5’ phosphate linkage. Also, modified by methylases.
Functions of 5’ 7-Methyl-G Cap
Prevents RNA degradation
o Stops nuclease from being able to recognize this.
Facilitates translation
o Cap serves as binding platform for translation machinery
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