Alternative splicing determines the intracellular localization of the novel nuclear protein Nop30 and its interaction with the splicing factor SRp30c.
We report on the molecular cloning of a novel human cDNA by its interaction with the splicing factor SRp30c in a yeast two-hybrid screen. This cDNA is predominantly expressed in muscle and encodes a protein that is present in the nucleoplasm and concentrated in nucleoli. It was therefore termed Nop30 (nucleolar protein of 30 kDa). We have also identified a related cDNA with a different carboxyl terminus. Sequencing of the NOP gene demonstrated that both cDNAs are generated by alternative 5' splice site usage from a single gene that consists of four exons, spans at least 1800 nucleotides, and is located on chromosome 16q21-q23. The alternative 5' splice site usage introduces a frameshift creating two different carboxyl termini. The carboxyl terminus of Nop30 is rich in serines and arginines and has been found to target the protein into the nucleus, whereas its isoform is characterized by proline/glutamic acid dipeptides in its carboxyl terminus and is predominantly found in the cytosol. Interaction studies in yeast, in vitro protein interaction assays, and co-immunoprecipitations demonstrated that Nop30 multimerizes and binds to the RS domain of SRp30c but not to other splicing factors tested. Overexpression of Nop30 changes alternative exon usage in preprotachykinin and SRp20 reporter genes, suggesting that Nop30 influences alternative splice site selection in vivo.
Stoss
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Max-Planck Institute of Neurobiology, Am Klopferspitz 18a, D-82152 Martinsried, Germany.
Schwaiger
F W
FW
Cooper
T A
TA
Stamm
S
S
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D051017:Apoptosis Regulatory Proteins; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002874:Chromosome Mapping; D002885:Chromosomes, Human, Pair 16; D003001:Cloning, Molecular; D018076:DNA, Complementary; D006801:Humans; D008969:Molecular Sequence Data; D009124:Muscle Proteins; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors
D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D018076:DNA, Complementary; D009124:Muscle Proteins; C112246:NOL3 protein, human; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors