Splicing

Question 1

heterogeneous nuclear RNA (hnRNA)

Answer 1

• includes RNAs that will become mRNA
• is a ribonucleoprotein
• RNA bound to many RNA-Binding proteins

Question 2

hnRNA must be processed to become mRNA

Answer 2

• a guanine is added at the 5’ UTR and then methylates, this prevents exonuclease degradation
• the 3’ UTR is polyadenylated
• pre-RNA is then processed by splicing

Question 3

Splice sites

Answer 3

GU-AG rule

Question 3

5’ Capping of RNA

Answer 3

• the first nucleotide is usually adenine
• Gppp5’-5’ApNp
• capping occurs during transcription shortly after the start
• it protects the RNA from nucleases

Question 4

Lariat structure

Answer 4

• a bond is formed between the 5’ Exon side of the 5’ GU site and the A withing the branch site
• the exon is cut and the 5’ GU loops over to bond with the A in the branch site
• the free 3’OH of the exon then attacks the exon at the 3’ AG splice site
• the ends of the two exons then join, leaving the Lariat structure

Question 5

small nuclear RNAs (snRNAs)

Answer 5

• exist as ribonucleoprotein particles
• are part of the spliceosome

Question 6

Branch point protein (BBP)

Answer 6

interacts with the branch point in the intron

Question 7

U2AF

Answer 7

binds to the intron region before the AG at the 3’ end of the intron

Question 8

Commitment Complex (E complex)

Answer 8

U1 snRNP, BBP, and U2Af form this
- identifies the splice sites
- folds the intron