RNA Splicing

Flashcards related to RNA Splicing lecture notes that cover key vocabulary and concepts.

pre-mRNA

The nuclear transcript that is processed by modification and splicing to give an mRNA.

RNA splicing

The process of excising introns from RNA and connecting the exons into a continuous mRNA.

Spliceosome

Splicing complex composed of protein and RNAs (including mRNA). Holds exons together for proper organization.

heterogeneous nuclear RNA (hnRNA)

RNA that comprises transcripts of nuclear genes made by RNA polymerase II; it has a wide size distribution and low stability.

hnRNP

The ribonucleoprotein form of hnRNA (heterogeneous nuclear RNA), in which the hnRNA is complexed with proteins.

5′ cap

Formed by adding a G to the terminal base of the transcript via a 5′–5′ link.

Splice sites

The sequences immediately surrounding the exon–intron boundaries. They are named for their positions relative to the intron.

GU-AG rule

Describes the requirement for these constant dinucleotides at the first two and last two positions of introns in pre-mRNAs (GU at the 5' end and AG at the 3' end).

Lariat

Formed when the intron is cleaved at the 5′ splice site, and the 5′ end is joined to a 2′ position at an A at the branch site in the intron.

small cytoplasmic RNAs (scRNA; scyrps)

RNAs that are present in the cytoplasm (and sometimes are also found in the nucleus).

small nuclear RNA (snRNA; snurps)

One of many small RNA species confined to the nucleus; several of them are involved in splicing or other RNA processing reactions.

small nucleolar RNA (snoRNA)

A small nuclear RNA that is localized in the nucleolus.

splicing factor

A protein component of the spliceosome that is not part of one of the snRNPs.

commitment complex (or E complex)

Contains U1 snRNP bound at the 5′ splice site and the protein U2AF bound to a pyrimidine tract between the branch site and the 3′ splice site.

exon junction complex (EJC)

A protein complex that assembles at exon–exon junctions during splicing and assists in RNA transport, localization, and degradation.

nonsense-mediated mRNA decay (NMD)

A pathway that degrades an mRNA that has a nonsense mutation prior to the last exon.

trans-splicing

Occurs in trypanosomes and worms where a short sequence (SL RNA) is spliced to the 5′ ends of many precursor mRNAs.