| Binding of a SART 3 tumor rejection antigen to a pre mRNA splicing factor RNPS 1 : a possible regulation of splicing by a complex formation . ^^^ To determine its biologic function , we employed a 2 hybrid screening in yeast for proteins interacting with SART 3 , and this method yielded a pre mRNA splicing factor ( RNA binding protein prevalent during the S phase or RNA binding protein with a serine rich domain [ RNPS 1 ] ) that activated both constitutive and alternative splicing of pre mRNA in vitro . ^^^ Interaction of SART 3 with RNPS 1 through the physical association of N terminal domains of RNPS 1 was confirmed by both in vitro pull down assay and immunoprecipitation assay . ^^^ Cotransfection of the 2 genes changed the distribution pattern of SART 3 from diffuse nucleoplasmic spreading to nuclear speckled regions in which the RNPS 1 was colocalized , suggesting a complex formation of the 2 proteins . ^^^ In cooperation with RNPS 1 , SART 3 stimulated the proximal alternative 3 ' splicing of a calcitonin dihydrofolate reductase chimeric minigene pre mRNA . ^^^ |