General splicing factor SF2/ASF promotes alternative splicing by binding to an exonic splicing enhancer.

Abstract

The general splicing factor SF2/ASF binds in a sequence-specific manner to a pm~ne-dch exonic splicing enhancer {ESE) in the last exon of bovine growth hormone (bGH) pre-mRNA. More importantly, SF2/ASF stimulates in vitro splicing of bGH intron D through specific interaction with the ESE sequences. However, another general splicing factor, SC35, does not bind the ESE sequences and has no effect on bGH intron D splicing. Thus, one possible function of SF2/ASF in alternative and, perhaps, constitutive pre-mRNA splicing is to recognize ESE sequences. The stimulation of bGH intron D splicing by SF2/ASF is counteracted by the addition of hnRNP A1. The relative levels of SF2/ASF and hnRNP A1 influence the efficiency of bGH intron D splicing in vitro and may be the underlying mechanism of this alternative pre-mRNA processing event in vivo.[Key Words: Alternative splicing; bovine growth hormone pre-mRNA; SF2/ASF; hnRNP A1; exonic splicing enhancer]Received September 3, 1993; accepted October 6, 1993.Pre-mRNA splicing requires accurate selection of 5' and 3' splice sites. For many genes, alternative splice sites can be selected from a single primary transcript to generate two or more mRNAs encoding multiple protein isoforms. Although alternative pre-mRNA splicing provides an important route for the regulation of gene expression, the underlying regulatory mechanisms remain largely uncharacterized.A central question in constitutive and alternative premRNA splicing concems the selection of specific splice sites. Introns are defined by the presence of a conserved 5' splice site, a 3' splice site, a polypyrimidine tract, and a less well-conserved branch site. Although these signals are required for splicing, they are insufficient to specify all introns. Several studies have shown that exon sequences can also play an important role in splice site Hoshijima et al. 1991}. The trans-acting factors encoded by the transformer (tra) and transformer 2 (tra2) genes together activate the 3' splice site upstream of the dsx female-specific exon 4 through interaction with six 13-nucleotide repeats present in the exon (Tian and Maniatis 1992). Thus, protein factors are capable of binding to exon sequences in a sequence-specific manner and affecting splicing of introns located some distance away from the protein-binding sites.A number of factors required for constitutive splicing have been shown to be involved in alternative splice site selection. The product of the Sex-lethal (Sxl) gene regulates alternative splicing of tra pre-mRNA by repressing the inclusion of exon 2 (Boggs et al. 1987). Recent results showed that Sx/inhibits the use of the 3' splice site upstream of exon 2 by blocking the binding of the essential splicing factor U2AF to the polypyrimidine tract (Valcarcel et al. 1993). Binding of U1 small nuclear ribonucleoprotein (snRNP) to a pseudo-5' splice site, as opposed to the authentic 5' splice site, has been implicated in the regulated alternative intron retention of Drosophila P-element pre-mRNA in somatic cells (Siebel et ...

Stage-specific changes in SR splicing factors and alternative splicing in mammary tumorigenesis

“…SR proteins have been observed to in¯uence splicing activity via their binding to both splice sites and special splicing accessory sequences known as enhancers (Zahler et al, 1993b;Fu, 1995;Manley and Tacke, 1996;Valcarcel and Green, 1996). Recent studies have indicated substrate-speci®c binding and activity for individual SR proteins (Fu, 1993;Sun et al, 1993;Zahler et al, 1993a;Ca ceres et al, 1994;Wang and Manley, 1995;Chandler et al, 1997;Liu et al, 1998). Furthermore, individual SR proteins have distinct tissue distributions (Zahler et al, 1992;Screaton et al, 1995;Ca ceres and Krainer, 1997).…”

Differential Regulation of Exonic Regulatory Elements for Muscle-specific Alternative Splicing during Myogenesis and Cardiogenesis

“…SF2/ASF and SC35, two SR proteins, differ in their ability to commit different pre-mRNAs to the splicing pathway (18). SF2/ASF, but not SC35, recognized sequences very similar to purine-rich elements found in various natural splicing enhancers (9,19). SRp40, another member of the SR protein group, binds specific ESE, and one study showed that phosphorylation of the arginrine/serine-rich domain is necessary for sequence-specific binding (20).…”

“…For example, a majority of exonic splicing enhancer (ESE) 1 elements have been reported to be abundant in purine nucleotides (14,15), and these elements have been shown to bind the splicing factor for control of alternative splicing. Serine/arginine-rich (SR) proteins, a group of splicing factors, play important roles both in ESE-independent and ESE-dependent splicing (8,9,16,17). SR proteins show RNA binding activity to each cis-acting element, as well as protein-protein interaction activity in the formation of a commitment complex of spliceosome (16).…”

Exonic splicing enhancers in fission yeast: functional conservation demonstrates an early evolutionary origin

“…Several classes of ESEs have been shown to bind SR (serine/arginine-rich) proteins (Lavigueur et al 1993;Sun et al 1993;Tian and Maniatis 1993). The mammalian SR protein family consists of 10 core members, not including isoforms (Screaton et al 1995) or related genes (Tupler et al 2001).…”