Exon identity established through differential antagonism between exonic splicing silencer-bound hnRNP A1 and enhancer-bound SR proteins.
SR proteins recognize exonic splicing enhancer (ESE) elements and promote exon use, whereas certain hnRNP proteins bind to exonic splicing silencer (ESS) elements and block exon recognition. We investigated how ESS3 in HIV-1 tat exon 3 blocks splicing promoted by one SR protein (SC35) but not another (SF2/ASF). hnRNP A1 mediates silencing by binding initially to a required high-affinity site in ESS3, which then promotes further hnRNP A1 association with the upstream region of the exon. Both SC35 and SF2/ASF recognize upstream ESE motifs, but only SF2/ASF prevents secondary hnRNP A1 binding, presumably by blocking its cooperative propagation along the exon. The differential antagonism between a negative and two positive regulators exemplifies how inclusion of an alternative exon can be modulated.
Zhu
J
J
Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
Mayeda
A
A
Krainer
A R
AR
D001483:Base Sequence; D001665:Binding Sites; D002457:Cell Extracts; D005091:Exons / Q000235:genetics*; D015696:Gene Products, tat / Q000235:genetics; D020868:Gene Silencing; D005816:Genetic Complementation Test; D005998:Glycine / Q000378:metabolism; D015497:HIV-1 / Q000235:genetics; D006367:HeLa Cells; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D006801:Humans; D007700:Kinetics; D008957:Models, Genetic; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012322:RNA Precursors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012326:RNA Splicing / Q000235:genetics*; D016601:RNA-Binding Proteins; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D012261:Ribonucleoproteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000172:deficiency / Q000378:metabolism; D000068103:Serine-Arginine Splicing Factors; D013379:Substrate Specificity; D054322:tat Gene Products, Human Immunodeficiency Virus
D002457:Cell Extracts; D015696:Gene Products, tat; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D009687:Nuclear Proteins; D012322:RNA Precursors; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D054322:tat Gene Products, Human Immunodeficiency Virus; C073288:SRSF2 protein, human; D000068103:Serine-Arginine Splicing Factors; D005998:Glycine