Small nuclear ribonucleoprotein complexes of Drosophila melanogaster.

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Abstract
The isolation and characterization of small nuclear ribonucleoproteins (snRNP) and correspondng small nuclear RNA (snRNA) species from nuclei of D. melanogaster are reported. Velocity sedimentation in sucrose gradients was used to partially fractionate the RNP; analysis of fractions so obtained suggests that, in general, one snRNP contains one snRNA. At least 11 spp. of snRNA are present in Drosophila nuclei; among them a potential mammalian U1 homolog based on sequence homology was identified. Autoimmune antiserum designated anti-Sm from patients with systemic lupus erythematosus recognizes nuclear antigens in Drosophila and precipitates 7 spp. of snRNP. The antigens in HeLa and Drosophila nuclei recognized by anti-Sm antibodies were identified and compared. Anti-Sm antibodies at least bind to a 26,000-dalton polypeptide in HeLa extracts and to 2 polypeptides (one of 18,000 daltons and one of 26,000 daltons) in Drosophila extracts. The 26,000-dalton polypeptide is evidently an evolutionarily conserved antigenic component of Drosophila and Hela snRNP.