Diverse Functions of RNAs Flashcards
all RNA’s are generated through transcription and are a ‘copy’ of a DNA portion, what are the 3 major differences between DNA and RNA?
- use ribose instead of deoxyribose
- uses uracil instead of thymine
- RNAs are single stranded
what are the two types of RNA associated with DNA modifications and chromatin remodeling?
- siRNAs
- long non-coding RNAs
what are the two types of RNA associated with RNA processing?
- snRNAs (small nuclear RNA)
- snoRNAs (small nucleolar RNAs)
what RNA type is associated with protein coding?
mRNA
what type of RNA is associated with mRNA turnover?
siRNAs (small interfering RNA)
what type of RNA is associated with translation regualtion?
miRNAs (microRNA)
what type of RNA is associated with ribosome structure in translation?
rRNAs (ribosomal RNA)
what type of RNA is associated with translation protein synthesis?
tRNAs
what are the two major control types that regulate protein production?
- transcriptional control
- post-transcriptional contorl
what are the two major transcriptional controls?
- chromatin structure
- initiation of transcription (RNA polymerase, general transcription factors, and specific transcriptional regulators)
what are the 3 post transcriptional control mechanisms in protein production?
- splicing efficiency
- mRNA stability
- translational control (initiation of translation, translation efficiency)
what are the three steps in mRNA processing?
- 5’ capping (addition of methylguanosine)
- splicing
- 3’ polyadenylation
what enzymes are involved in 5’ capping during mRNA processing?
- phosphatase (removed 5’-P)
- guanyl transferase (adds G in 5’-5’ orientation)
- methyltransferase (adds methyl-group to base)
how does mRNA processing occur?
RNA Pol. II contains a long tail with tandem repeats with Ser at 2 and 5 position. The 5 position is phosphorylated during transcription initiation allowing the capping proteins to bind to Pol. The proteins then ‘jump’ to the 5’ end of the mRNA as it emerges from RNA Pol. coupling transcription with mRNA processing. The same principle is used for splicing and 3’-modification.
what is the two major steps to mRNA splicing?
- adenine base (near 3’ end of intron) attacks the 5’-end of the intron cutting it which covalently binds the 5’-base of teh intron forming a lariat
- the released 3’-OH of the exon reacts w the 3’ end of the intron. this cuts the last base of the intron and releases the intron as a lariate. following this the exon joins with the released 5’-phosphate
what are the two sequences of mRNA that be conserved for splicing to occur?
- intron/exon boundaries
- branch point
in mRNA splicing, splicing is facilitated by a large complex, what is it called?
a spliceosome
how many snRNP are present in a spliceosome?
5 snRNP
for each snRNP in a spliceosome, how many proteins are there?
7 proteins with 1 snRNA
snRNAs are the core of the spliceosome and fold into a complex 3D-structure, what does it bind to form the snrNP?
it binds Sm protein ring to form snRNP
in mRNA splicing what does U1 snRNP bind?
U1 snRNP base pairs to 5’-end of the intron to be spliced out
in mRNA splicing there is a 5’-splic rearrangement where U1 is exchanged for U4/6 snRNP. why does this occur?
is a check and re-check strategy to ensure that the appropriate splice site is being targeted
in mRNA splicing there is a branch point site rearrangement: BBB-> U2- snRNP. what does this achieve?
U2 snRNA pairs with branch-point, excluding and exposing the adenine that will form the lariat. this acts as another double check in the splicing process.
what happens in mRNA splicing after both the 5’ splice rearrangement and the branch point site rearrangement have occurred?
U6 and U2 snRNA can pair with each other. this brings branch point A to exposed 5’ end of the intron allowing A to attach the 5’-G of intron and cause cleavage at the 5’ end of the intron.
