Mammalian splicing factor SF1 interacts with SURP domains of U2 snRNP-associated proteins

Abstract

Splicing factor 1 (SF1) recognizes the branch point sequence (BPS) at the 3′ splice site during the formation of early complex E, thereby pre-bulging the BPS adenosine, thought to facilitate subsequent base-pairing of the U2 snRNA with the BPS. The 65-kDa subunit of U2 snRNP auxiliary factor (U2AF65) interacts with SF1 and was shown to recruit the U2 snRNP to the spliceosome. Co-immunoprecipitation experiments of SF1-interacting proteins from HeLa cell extracts shown here are consistent with the presence of SF1 in early splicing complexes. Surprisingly almost all U2 snRNP proteins were found associated with SF1. Yeast two-hybrid screens identified two SURP domain-containing U2 snRNP proteins as partners of SF1. A short, evolutionarily conserved region of SF1 interacts with the SURP domains, stressing their role in protein–protein interactions. A reduction of A complex formation in SF1-depleted extracts could be rescued with recombinant SF1 containing the SURP-interaction domain, but only partial rescue was observed with SF1 lacking this sequence. Thus, SF1 can initially recruit the U2 snRNP to the spliceosome during E complex formation, whereas U2AF65 may stabilize the association of the U2 snRNP with the spliceosome at later times. In addition, these findings may have implications for alternative splicing decisions.

Vemurafenib-resistant BRAF selects alternative branch points different from its wild-type BRAF in intron 8 for RNA splicing

“…Recent genome-wide BP mapping studies indicate that a large proportion of introns have more than one BP, generally clustered in close proximity in relation to the 3′ splice site [ 27 , 38 ], although a BP could be found in rare case further upstream of a 3′ splice site [ 27 , 38 ]. Since the predicted -51C [ 11 ] from the 3′ splice site of intron 8 identified by ESEfinder [ 34 ] or by Human Splice Finder [ 28 ] was not mapped as an authentic BP in this study, our data imply that the observed mutations (-435 C-to-A and -51 C-to-G) in the mt BRAF pre-mRNA might disrupt the binding of trans -acting factors, such as SRSF6 (SRp55) [ 11 , 39 , 40 ] and SF3b/3a [ 41 – 45 ], to the -51 region and thereby prevent the recruitment of SF1 and U2 snRNA [ 46 – 48 ] to select an authentic distal BP for splicing of BRAF RNA. Consequently, loss of splicing factor binding to the -51 region and activation of a proximal BP usage might lead to skipping of exons 4–8 in splicing of mt BRAF.…”

Extensive cryptic splicing upon loss of RBM17 and TDP43 in neurodegeneration models

“…One of the RBPs that has been implicated in cancer and a neurodegenerative disease, but has not been studied in great detail, is RNA-binding motif protein 17 (RBM17) (15,16). Originally identified as a component of the spliceosome complex, it interacts with splicing factors U2AF2, SF1 and SF3B1 (17)(18)(19); our lab has also discovered that RBM17 binds Ataxin-1 in a polyglutamineand phosphorylation-dependent manner (15). Limited studies on the splicing functions of RBM17 so far have suggested a role in alternative splicing.…”

Regulating Divergent Transcriptomes through mRNA Splicing and Its Modulation Using Various Small Compounds

“…SURP domains interact with SF1, and G-patch domains were shown to activate RNA helicases for ATP hydrolysis. Both domains are required for BP recognition by the SF3B1-containing U2 snRNP [103][104][105]. These findings strongly suggest that SUGP1 is involved in the BP recognition process.…”