Lecture 16: Post-Transcriptional Control in Eukaryotes Flashcards
In eukaryotes, how does phosphorylation of eIF2 slow down protein synthesis?
Phosphorylated eIF2 cannot change its GDP to GTP in order to activate, so it holds onto eIF2B - eIF2B is need to activate other eIF2’s, which can no longer get it
What is the IRES?
Internal ribosome entry site, provides opportunities for translation control by allowing translation to occur without a 5’ cap and eIF4E
How do viruses use the IRES?
Some viruses have a protease that destroys eIF4E and prevents translation, so viral RNA forms IRES so they can bind eIF4G and start translating)
How do some human genes use the IRES to counter viruses?
If viruses degrade eIF4E, the human RNA can use IRES to translate as normal
Possible fates of mRNA molecules
P-body (degradation), stress granule (storage), or being used in translation
What are the two mechanisms of eukaryotic mRNA decay?
Gradual poly(A) shortening by exonucleases (3’ to 5’), or decapping followed by rapid 5’ to 3’ degradation
What helps determine half life of each mRNA?
The specific 3’ UTR sequence
Purpose and location of deadenylase
Shortens the 3’ Poly(A) tail, and associates with the 5’ cap
Basic process of degradation by miRNA
miRNA serve as guide sequences that find target RNAs and mark them for destruction/degradation
What is an RISC?
RNA-induced silencing complex
Main purpose of small interference RNAs (siRNAs)
Mark mRNAs for degradation or cause transcriptional silencing (by attracting proteins that use histone modification to induce heterochromatin formation and prevent further transcription)
What is an RITS complex?
RNA-induced transcriptional silencing complex
Types of alternative RNA splicing
exon skipping, intron retention, alternative 5’ splice site, alternative 3’ splice site
