Modulation of P-element pre-mRNA splicing by a direct interaction between PSI and U1 snRNP 70K protein.
P-element somatic inhibitor (PSI) is a KH domain-containing splicing factor highly expressed in Drosophila somatic tissues. Here we have identified a direct association of PSI with the spliceosomal U1 small nuclear ribonucleoprotein (snRNP) particle in somatic nuclear extracts. This interaction is mediated by highly conserved residues within the PSI C-terminal AB motif and the U1 snRNP-specific 70K protein. Through the AB motif, PSI modulates U1 snRNP binding on the P-element third intron (IVS3) 5' splice site and its upstream exonic regulatory element. Ectopic expression experiments in the Drosophila female germline demonstrate that the AB motif also contributes to IVS3 splicing inhibition in vivo. These data show that the processing of specific target transcripts, such as the P-element mRNA, is regulated by a functional PSI-U1 snRNP interaction in Drosophila.
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Department of Molecular and Cell Biology, University of California, Berkeley, 401 Barker Hall-3204, Berkeley, CA 94720, USA.
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D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002458:Cell Fractionation; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics; D005260:Female; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D015151:Immunoblotting; D019476:Insect Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010053:Ovary / Q000737:chemistry; D011485:Protein Binding; D012326:RNA Splicing / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000378:metabolism*; D016415:Sequence Alignment
D029721:Drosophila Proteins; D019476:Insect Proteins; D009687:Nuclear Proteins; C092281:PSI protein, Drosophila; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D017412:Ribonucleoprotein, U1 Small Nuclear