Protein IsoformsAlternative SplicingMolecular Sequence DataExonsRNA SplicingAmino Acid SequenceRNA Splice SitesBase SequenceRNA, MessengerReverse Transcriptase Polymerase Chain ReactionProtein Structure, TertiaryCell LineProtein BindingIntronsIsoenzymesRNA PrecursorsRNA IsoformsDNA, ComplementaryCloning, MolecularMutationIsomerismSequence Homology, Amino AcidTransfectionSpliceosomesDNA PrimersTranscription, GeneticBlotting, WesternPolymerase Chain ReactionRibonucleoprotein, U1 Small NuclearHeLa CellsSequence AlignmentCOS CellsCells, CulturedRecombinant ProteinsGene Expression RegulationRNA, Small NuclearGene ExpressionOrgan SpecificityRNA-Binding ProteinsNuclear ProteinsTissue DistributionBinding SitesMembrane ProteinsSequence Homology, Nucleic AcidGenetic VariationSignal TransductionMyosin Heavy ChainsProtein Kinase CBlotting, NorthernSequence Deletion