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mol. genetics ch 19

mRNA stability and localization

QuestionAnswer
where is mRNA regulatory information typically found within the mRNA? the untranslated regions of mRNA
whar are ribonucleases? RNA-degrading enzymes
what is the difference between an exonuclease and an endonuclease? an exonuclease removes terminal ribonucleotides from RNA, while endonucleases cleaves RNA at internal site(s)
what is a half-life? the time it takes for half a sample of something to decay.
does half-life vary between different mRNAs? yes, in ecoli it can range from 20 seconds to 90 minutes
what is the advantage of having unstable mRNAs? the ability to rapidly change the output of translation through changes in mRNA synthesis
what are RNPs? ribonucleoprotein particles
what are RNPs used for? they are key regulators in post-transcriptional gene expression, RNA processing, and structural support within the cell
what is a regulon? group of genes/operons located at different points of a genome regulated by the same transcription factor
what is a polyribosome (polysome)? one mRNA with multiple ribosomes
how is prokaryotic mRNA typically degraded? a combination of endonuclease and 3' -> 5' exonuclease activities
what are the steps for prokaryotic mRNA degradation? removal of pyrophosphate from 5' terminus, stimulation of catalytic activity of an endonuclease which makes an initial cut near 5' end of mRNA, degradation of upstream fragment by exonuclease
how is eukaroytic mRNA typically degraded? deadenylation, decapping, and exonucleolytic degradation
what are the two main degradation (eukaryotic) pathways? first pathway: digestion of the poly(A) tail down about 10-12 A residues triggers de-capping at the 5’ end of the mRNA. second pathway: de-adenylation is followed by 3’-5’ exonuclease digestion of the body of the mRNA.
what are P bodies? particles containing multiple mRNAs and proteins involved in mRNA degradation and translational repression (occurring in many copies in the cytoplasm of eukaryotes)
what are destabilizing elements? specific elements that accelerate mRNA decay
what are stabilizing elements? elements that reduce mRNA decay
what is an RNA surveillance system? system that destroys aberrant nuclear RNAs and involved two activities: identify and tag the RNA, and destroy it
what is TRAMP? major nuclear complex responsible for targeting aberrant RNAs to the exosome and facilitates exonuclease activity
how does TRAMP work? . It works by polyadenylating the 3' end of target RNAs and unwinding them, facilitating efficient degradation by the Rrp6-containing core exosome.
what is an exosome? extracellular vesicles that mediate intercellular communication
what is nonsense-mediated decay? targets mRNAs containing a premature termination codon (PTC)
what is nonstop decay? targets mRNAs lacking an in-frame termination codon and requires a set of SKI proteins
what is no-go decay? targets mRNAs with stalled ribosomes in their coding regions (due to secondary structures)
how is mRNA localized to a particular area of the cell? transporting, anchoring, and translating messenger RNA (mRNA) at specific subcellular locations rather than distributing it evenly throughout the cell
what are the three main mechanisms for mRNA localization? mRNA is uniformly distributed but degraded/translationally repressed, mRNA is initially freely diffusible but becomes trapped, mRNA is actively transported
which of the three mechanisms for mRNA localization is predominant? active transport by way of motor proteins along cytoskeletal tracks
what is diffusion? movement of particles from high concentration to lower concentration
what is active transport? energy dependent movement of molecules against a concentration gradient, from low to high concentration
Created by: angievelasco
 

 



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