U2AF next recruits U2 sn RNP to the branch point to form the pre-spliceosome complex A.
The 3′-end processing of pre-m RNAs involves two tightly coupled steps: 3′-end cleavage and polyadenylation.
Although slower, S2A RNAP II was able to transcribe.
However, it failed to recruit splicing components such as U2AF65 and U2 sn RNA to transcription sites, although the recruitment of U1 sn RNA was not affected.
Splicing is catalyzed by the spliceosome, a large ribonucleoprotein (RNP) complex.
The spliceosome comprises five small nuclear RNP (sn RNP) particles and many auxillary factors.