title: Characterization and primary structure of the poly(C)-binding heterogeneous nuclear ribonucleoprotein complex K protein.
abstract: At least 20 major proteins make up the ribonucleoprotein (RNP) complexes of heterogeneous nuclear RNA (hnRNA) in mammalian cells. Many of these proteins have distinct RNA-binding specificities. The abundant, acidic heterogeneous nuclear RNP (hnRNP) K and J proteins (66 and 64 kDa, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) are unique among the hnRNP proteins in their binding preference: they bind tenaciously to poly(C), and they are the major oligo(C)- and poly(C)-binding proteins in human HeLa cells. We purified K and J from HeLa cells by affinity chromatography and produced monoclonal antibodies to them. K and J are immunologically related and conserved among various vertebrates. Immunofluorescence microscopy with antibodies shows that K and J are located in the nucleoplasm. cDNA clones for K were isolated, and their sequences were determined. The predicted amino acid sequence of K does not contain an RNP consensus sequence found in many characterized hnRNP proteins and shows no extensive homology to sequences of any known proteins. The K protein contains two internal repeats not found in other known proteins, as well as GlyArgGlyGly and GlyArgGlyGlyPhe sequences, which occur frequently in many RNA-binding proteins. Overall, K represents a novel type of hnRNA-binding protein. It is likely that K and J play a role in the nuclear metabolism of hnRNAs, particularly for pre-mRNAs that contain cytidine-rich sequences.
authors.affiliation: Howard Hughes Medical Institute, University of Pennsylvania School of Medicine, Philadelphia 19104-6148.
authors.forename: M J
authors.initials: MJ
authors.lastname: Matunis
authors.forename: W M
authors.initials: WM
authors.lastname: Michael
authors.forename: G
authors.initials: G
authors.lastname: Dreyfuss
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002417:Cattle; D002460:Cell Line; D002846:Chromatography, Affinity; D006224:Cricetinae; D004247:DNA; D015180:Electrophoresis, Gel, Two-Dimensional; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D006801:Humans; D015151:Immunoblotting; D008969:Molecular Sequence Data; D011066:Poly C / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D012261:Ribonucleoproteins; C072074:HNRNPK protein, human; D011066:Poly C; D004247:DNA