Association of two nuclear proteins, Npw38 and NpwBP, via the interaction between the WW domain and a novel proline-rich motif containing glycine and arginine.
We have previously reported a nuclear protein possessing a WW domain, Npw38 (Komuro, A., Saeki, M., and Kato, S. (1999) Nucleic Acids Res. 27, 1957-1965). Here we report a Npw38-binding protein, NpwBP, isolated from HeLa cell nuclear extracts and its characterization using a cloned cDNA. NpwBP contains two proline-rich regions that are capable of binding to the WW domain of Npw38. The binding analysis using an oligopeptide-immobilized membrane revealed that the WW domain of Npw38 preferentially recognizes a short proline-rich sequence, PPGPPP, surrounded by an arginine residue, so we named it a PGR motif. Localization analysis using green fluorescent protein fusion protein and immunostaining showed that Npw38 and NpwBP are colocalized in the same subnuclear region. Coimmunoprecipitation experiments confirmed the association between Npw38 and NpwBP, which were expressed as epitope-tagged forms in COS7 cells. Furthermore, the N-terminal region of NpwBP has binding ability for poly(rG) and G-rich single-stranded DNA. These results suggest that NpwBP is a physiological ligand of Npw38 and that the Npw38-NpwBP complex may function as a component of an mRNA factory in the nucleus.
Komuro
A
A
Kato Cytoprotein Network Project, ERATO, Japan Science and Technology Corporation (JST), c/o Sagami Chemical Research Center, Nishi-Ohnuma 4-4-1, Sagamihara, Kanagawa 229-0012, Japan.
Saeki
M
M
Kato
S
S
D000595:Amino Acid Sequence; D001120:Arginine; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D005998:Glycine; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D011392:Proline; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C119246:PQBP1 protein, human; D011993:Recombinant Fusion Proteins; C403130:nuclear protein wBP; D001120:Arginine; D011392:Proline; D005998:Glycine