ISOLATION AND CHARACTERIZATION OF A NEW 110 KDA HUMAN NUCLEAR RNA-BINDING PROTEIN (P110(NRB))

RNA-protein interactions play key roles in many fundamental cellular p rocesses such as RNA processing, RNA transport, and RNA translation. D uring our attempts to isolate the human U6 small nuclear RNA capping e nzyme, we identified a new 110 kDa nuclear RNA-binding protein, design ated p110(nrb). The full-length cDNA clone for p110(nrb) was character ized, and it encodes a 963 amino acid polypeptide. It is a highly acid ic protein (pI 5.28) and the carboxyl terminal portion contains two co nserved RNP motifs. A databank search found a putative C. elegans prot ein that might be the p110(nrb) homologue. The p110(nrb) was overexpre ssed as a glutathione S-transferase fusion protein in insect Sf9 cells , purified by affinity chromatography and injected into rabbits to pro duce specific polyclonal antibodies. Immunofluorescent staining showed that p110(nrb) is distributed evenly throughout the nucleoplasm. Nort hern blots showed that the mRNA is expressed in all tissues examined. An in vitro RNA-binding assay showed that p110(nrb) bound to RNA. Thes e data suggest that p110(nrb) may play a role in the metabolism of nuc lear RNA. (C) 1998 Elsevier Science B.V. All rights reserved.