Lecture 10: The Splicing Process in mRNA

Pre-mRNA

Initial RNA transcript before splicing occurs.

Introns

Non-coding sequences removed during mRNA splicing.

Exons

Coding sequences retained in mature mRNA.

5' Cap

Modified guanine nucleotide added to pre-mRNA.

U1 SnRNP

Binds to 5' splice site for splicing initiation.

snRNA

Small nuclear RNA involved in splicing.

U2AF

U2 Associated Factor, binds to poly(Y) tract.

SR Proteins

Splicing regulator proteins that assist in splice site recognition.

Branch Point

Adenosine site critical for lariat formation.

U5 SnRNP

Binds near both 5' and 3' splice sites.

U4/U6 Complex

Pre-activated snRNP complex involved in splicing.

U6 Ribozyme

Catalytic RNA that cleaves RNA during splicing.

U4 Inhibitor

Prevents U6 activity until splicing is ready.

Lariat Intermediate

Looped structure formed during intron removal.

Cleavage of 5' Site

First step in splicing, facilitated by U6.

Ligation of Exons

Joining of exons after intron removal.

ESE (Exonic Splicing Enhancers)

Enhancers that promote recognition of weak splice sites.

ESS (Exonic Splicing Silencers)

Silencers that inhibit strong splice site recognition.

Alternative Splicing

Process allowing multiple mRNA variants from one gene.

Positive Regulation

Activation of weak splice sites by SR proteins.

Negative Regulation

Repression of strong splice sites without signals.

Torpedo Model

Termination mechanism involving exonuclease catching RNA polymerase.