Characterisation of two major cellular poly(rC)-binding human proteins, each containing three K-homologous (KH) domains.
We have revealed and characterised two nucleic-acid-binding proteins, termed PCBP-1 (M(r) 37,525, pI 7.07) and PCBP-2 (M(r) 38,579, pI 6.76), that together with heterogeneous ribonucleoparticle (hnRNP)-K correspond to the major cellular poly(rC)-binding proteins. mRNA for both PCBPs were detected in all the human tissues analysed. Both proteins contain three K-homologous (KH) domains which share similarity with other KH domain proteins, including the fragile-X protein FMR1, and which are positioned as in hnRNP-K and nova, i.e. with two closely spaced domains at the N-terminus and one at the C-terminus. PCBPs do not contain RGG boxes or any other known nucleic-acid-binding motifs. Expression in the vaccinia virus system showed that both proteins are post-translationally modified in vivo, a fact that was confirmed by [32P]orthophosphate labelling. Northwestern-blot analysis showed that the non-phosphorylated forms bind tenaciously to poly(rC) in vitro, while significantly less binding was observed for the phosphorylated variants. Escherichia coli expressed proteins also bound poly(rG), albeit at a lower level. In addition, PCBP-2 bound poly(rU), whereas very little binding to poly(rA) was observed for both proteins.
Leffers
H
H
Danish Centre for Human Genome Research, Institute of Medical Biochemistry, Aarhus University, Denmark.
Dejgaard
K
K
Celis
J E
JE
D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000378:metabolism; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D006801:Humans; D008969:Molecular Sequence Data; D009696:Nucleic Acids / Q000378:metabolism; D011066:Poly C / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors; D014616:Vaccinia virus / Q000235:genetics
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D009696:Nucleic Acids; C094604:PCBP1 protein, human; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D011066:Poly C