BP

GO:0000350

generation of catalytic spliceosome for second transesterification step

Conformational rearrangement of the spliceosomal complex containing the RNA products from the 1st step of splicing to form the catalytic site for the second step of splicing.

IBA

BP

GO:0006397

mRNA processing

Any process involved in the conversion of a primary mRNA transcript into one or more mature mRNA(s) prior to translation into polypeptide.

TAS

BP

GO:0008380

RNA splicing

The process of removing sections of the primary RNA transcript to remove sequences not present in the mature form of the RNA and joining the remaining sections to form the mature form of the RNA.

TAS

BP

GO:0071048

nuclear retention of unspliced pre-mRNA at the site of transcription

The process involved in retention of incorrectly or incompletely spliced pre-mRNA within the nucleus at the site of transcription.

IBA

CC

GO:0005634

nucleus

A membrane-bounded organelle of eukaryotic cells in which chromosomes are housed and replicated. In most cells, the nucleus contains all of the cell's chromosomes except the organellar chromosomes, and is the site of RNA synthesis and processing. In some species, or in specialized cell types, RNA metabolism or DNA replication may be absent.

TAS

CC

GO:0005681

spliceosomal complex

Any of a series of ribonucleoprotein complexes that contain snRNA(s) and small nuclear ribonucleoproteins (snRNPs), and are formed sequentially during the spliceosomal splicing of one or more substrate RNAs, and which also contain the RNA substrate(s) from the initial target RNAs of splicing, the splicing intermediate RNA(s), to the final RNA products. During cis-splicing, the initial target RNA is a single, contiguous RNA transcript, whether mRNA, snoRNA, etc., and the released products are a spliced RNA and an excised intron, generally as a lariat structure. During trans-splicing, there are two initial substrate RNAs, the spliced leader RNA and a pre-mRNA.

TAS

CC

GO:0005682

U5 snRNP

A ribonucleoprotein complex that contains small nuclear RNA U5.

IBA

CC

GO:0016607

nuclear speck

A discrete extra-nucleolar subnuclear domain, 20-50 in number, in which splicing factors are seen to be localized by immunofluorescence microscopy.

IEA

CC

GO:0046540

U4/U6 x U5 tri-snRNP complex

A ribonucleoprotein complex formed by the association of the U4/U6 and U5 small nuclear ribonucleoproteins.

IBA

CC

GO:0071021

U2-type post-spliceosomal complex

A spliceosomal complex that is formed following the second splicing event and contains the spliced product, the excised intron, and three snRNPs, including U5.

IBA

MF

GO:0000386

second spliceosomal transesterification activity

Catalysis of the second transesterification reaction of spliceosomal mRNA splicing. Ligation of the two exons occurs via a transesterification reaction where the free 3'-hydroxyl group of the 5' exon is the nucleophile attacking the 3' splice site. Non-expressed sequences are now detached from the exons. In cis splicing, the intron is in a lariat structure.

IBA