Lecture 27 - Post-transcriptional Control, Control of Gene Expressions 2: Flashcards
What is alternative splicing?
What are the two control mechanisms for alternative splicing?
L27 S4-5
-selective inclusion/exclusion of exons from the same gene transcript to form different mRNAs
Control mechanisms:
- negative control: repressors block splicing
- positive control: activators direct splicing
How can gene expression be regulated by altering RNA stability?
L27 S7-8
- degradation of poly-A tail
- removal of 5 prime cap
What is an IRE and an IRP?
L27 S16
IRE:
- iron responsive element
- mRNA structure that acts as recognition site for IRP
IRP:
- iron responsive regulatory protein
- protein that binds IRE
- ie. aconitase
How do IREs and IRPs regulate iron related mRNAs?
L27 S17-20
Iron starvation:
- IRP binds 5’ IRE on ferritin mRNA blocking translation
- IRP binds 3’ IRE on transferrin mRNA preventing degradation
Iron excess:
- iron bound IRP does not bind ferritin mRNA allowing translation
- iron bound IRP does not bind transferrin mRNA allowing degradation
How do microRNAs regulate gene expression?
L27 S21
-contain complimentary sequences for specific mRNAs and block transcription or target for degradation
How do chaperones regulate proteins post-transcriptionally?
L27 S31+33
-ensure that proteins are folded into proper three dimensional shape for their function
How do proteasomes regulate proteins post-transcriptionally?
L27 S34-38
- proteasomes selectively destroy proteins marked for degradation
- proteins are targeted by addition of ubiquitin to abnormally folded proteins
- cap area on proteasome recognizes ubiquinated proteins
How does DNA methylation regulate gene expression?
- DNA methylation prevents gene expression
- methylation occurs at CG regions and is maintained following DNA replication
What is genomic imprinting?
L27 S51-52
- differential expression of genes based on parent of origin
- based on inherited pattern of DNA methylation
- eg. Prader Willi syndrome
