Ch. 13 - non-coding RNAs Flashcards
history of non-coding RNAs
- ncRNAs were first linked to disease in 2001
- compared to coding RNAs linked to disease in 1909
6 main functions of ncRNAs
- scaffold
- guide
- alteration of protein function or stability
- ribozyme
- blocker
- decoy
scaffold ncRNA
- bind to multiple components such as proteins, act as scaffold for formation of a complex
guide ncRNA
- guide a molecule to a specific location in a cell
- ex: make bind a protein and take it to a specific site in DNA
- must have binding site for both the protein and the DNA
ncrNA alteration of protein function or stability
- when the ncRNA binds to protein and can alter the structure
3 things it may affect:
1. the ability of the protein to act as a catalyst
2. the ability of the protein to bind other molecules
3. stability of the protein
ribozymes
ncRNA with catalytic function
blocker ncRNA
- physically prevents or blocks a cellular process from happening
decoy ncRNA
- recognize other ncRNAs and bind to them, preventing them from working
Xist
type of ncRNA
- coats one of the X chromosomes in female mammals and plays a role in its compaction and resulting inactivation
HOTAIR
Hox transcript antisense intergenic RNA
- gene located within the HoxC cluster
- contains the antisense from the HoxC genes
- actas as a scaffold for protein complexes that covalently modify histone proteins
- modifications from HOTAIR inhibit transcription, directly or indirectly
two ways HOTAIR can inhibit transcription
- directly inhibiting the ability of RNA polymerase to transcribe the gene
- can prevent RNA polymerase from forming a pre initiation complex - can attract other chromatin-modifying enzymes to the target gene
- would lead to further changes in chromatin structure that inhibit transcription
miRNA
microRNAs
- ncRNAs transcribed from endogenous eukaryotic genes
- play key roles in regulating gene expression, particularly during embryonic development
- partially complementary to mRNAs
- inhibits mRNA in RNA interference (RNAi)
siRNAs
small-interfering RNAs
- come from exogenous sources (viruses that infect a cell or from researchers)
- usually a perfect match for mRNA
- degrades mRNA
- plays key role in preventing certain types of viral infections
- also important tool for study molecular biology
RNA interference
- found in most eukaryotic species
- can be promoted by miRNAs or siRNAs
- miRNA and siRNA is cut by dicer to a sequence 20-25bp long
- sequence binds with RISC, which inhibits translation or degrades the mRNA
RISC
RNA-induced silencing complex
- inhibits translation or degrades the mRNA
two roles of SRP RNA
- provide scaffold for the binding of SRP protein(s)
- after SRP binds to the SRP receptor in the ER membrane, it stimulates proteins in the SRP and SRP receptor to hydrolyze GTP
- allows SRP to release
adaptation in crispr
- occurs after bacterial cell has been exposed to bacteriophage
- Cas1/2 complex cleaves bacteriophage DNA and inserts it into the Crispr gene
expression in crispr
- subsequent bacteriophage infection results in the expression phase
- genes encoding pre-crRNA and tracrRNA are transcribed
- complementary base pairing between crRNA and tracrRNA repeats allows formation of the tracrRNA-crRNA complex
- complex binds to Cas9 protein
