Ch. 14 RNA Processing Flashcards
ribonucleotides
NTPs
deoxyribonucleotides
dNTPs
ribosomes
rRNAs
promoter
- initial binding site of the RNA polymerase
- specifies which polymerase is used for the different classes of genes to be transcribed
transcription initiation
- TF2D and TBP binds with TATA box and partially unwinds DNA
- TF2s bind
- Polymerase is positioned over start site
- transcription bubble formed
- Polymerase starts transcribing
pre mRNA. what are the components?
pre messenger RNA
5’ untranslated region (UTR) needed for ribosome binding
receives 5’ methyl cap
3’ untranslated region (UTR) needed for mRNA stability and translation
AAAA tail
protein coding region
how do we process pre-mRNA?
- add 5’ methyl cap (says “don’t degrade me”)
- required to initiate translation
- adds stability
- influences intron splicing
- added during transcription - add Poly (A) tail
- “polyadenylation”
- adds stability
- facilitates attachment of ribosome to mRNA
- helps export mRNA out of nucleus - intron splicing
how do we add 5’ methyl cap?
- remove phosphate from 5’ nucleotide
- add G (guanine)
- methylation of added G
- methylation of a few of the nucleotides at the 5’ end on their 2 - OH
* only place where we see 5’ to 5’ bond*
how do we add Poly (A) tail?
50 to 250 A’s added to the end of the transcript
-not coded in the DNA (post transcriptional modification)
introns
non-coding regions of mRNA
not all of the mRNA codes into proteins!
spliceosome
carries out mRNA splicing
- composed of 5 RNA molecules (snRNAs, small nuclear RNAs) and almost 300 proteins
- U1, U2, U4, U5, U6 - different types of snRNAs that play a role in splicing
alternative splicing
the same gene produces identical pre-mRNAs but are alternatively processed
- important source of protein diversity!
- 60% of human genes are alternatively spliced
