RNA-Based Regulation Flashcards
(36 cards)
What are noncoding RNAs? What are some examples?
Noncoding RNAs are RNA molecules that do not encode proteins. Examples include microRNAs and long noncoding RNAs.
What are small RNAs? How do they exert their effects?
Small RNAs are short RNA molecules that regulate gene expression. They exert their effects by base-pairing with target mRNAs.
What four mechanisms are used by sRNAs to alter translation of mRNA?
The four mechanisms are: 1) binding to mRNA to block ribosome access, 2) promoting ribosome binding, 3) altering mRNA structure, and 4) facilitating mRNA degradation.
What are some examples of cellular processes modulated by sRNAs?
Examples include stress responses, virulence, and metabolic regulation.
What are RNA chaperones?
RNA chaperones are proteins that assist in the proper folding and assembly of RNA molecules.
What exactly is a riboswitch?
A riboswitch is a segment of RNA that can change its structure in response to a specific metabolite, regulating gene expression.
How are ribozymes different from riboswitches?
Ribozymes are RNA molecules that catalyze biochemical reactions, while riboswitches regulate gene expression by changing conformation.
Where, on a mRNA molecule, are riboswitch domains typically located?
Riboswitch domains are typically located in the 5’ untranslated region (5’ UTR) of mRNA.
How do riboswitches work?
Riboswitches work by binding small metabolites, causing a conformational change that affects the mRNA’s ability to be translated.
What are some examples of cellular processes regulated by riboswitches?
Examples include amino acid biosynthesis and vitamin metabolism.
Although most riboswitches regulate translation, a few can cause premature termination of transcription. How is this achieved?
This is achieved by forming a terminator structure in the mRNA that signals RNA polymerase to stop transcription.
What exactly is attenuation?
Attenuation is a regulatory mechanism that controls transcription termination based on the presence of specific metabolites.
What role does the leader of a mRNA molecule play in the attenuation process?
The leader sequence contains regulatory elements that determine whether transcription will continue or terminate.
Why are eukaryotic cells unable to use attenuation to regulate transcription?
Eukaryotic cells cannot use attenuation because transcription and translation occur in different cellular compartments.
Where is the leader sequence typically located in an operon?
The leader sequence is typically located at the beginning of the operon, upstream of the coding sequences.
In the example of the trp operon, how does translation of the leader sequence lead to the termination of transcription of the rest of the operon?
Translation of the leader sequence allows the formation of a terminator structure, which signals RNA polymerase to stop transcription.
In the example of the trp operon, how does the inability to translate the leader sequence permit the entire operon to be transcribed?
If the leader sequence cannot be translated, a different structure forms that allows RNA polymerase to continue transcription.
In the example of the trp operon, why does a low level of tryptophan cause the ribosome to stall during the translation of the leader sequence?
A low level of tryptophan leads to insufficient tryptophan-tRNA, causing the ribosome to stall.
What is feedback inhibition?
Feedback inhibition is a regulatory mechanism where the end product of a pathway inhibits an earlier step in the pathway.
What is an allosteric site (on an enzyme)? How is the allosteric site different from the enzyme’s active site?
An allosteric site is a site on an enzyme where molecules can bind and alter enzyme activity. It differs from the active site, where substrate binding occurs.
What are isoenzymes?
Isoenzymes are different forms of an enzyme that catalyze the same reaction but have different properties.
What is the advantage of having a pathway controlled by different isoenzymes?
The advantage is that it allows for regulation of the pathway under different conditions or in different tissues.
What is covalent modification?
Covalent modification is a process where a chemical group is added or removed from an enzyme, altering its activity.
What five functional groups can be attached to proteins/enzymes to regulate their activity?
The five functional groups are phosphate, methyl, acetyl, ubiquitin, and adenyl groups.
