Characterisation of two major cellular poly(rC)-binding human proteins, each containing three K-homologous (KH) domains

Eur J Biochem. 1995 Jun 1;230(2):447-53.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cell Line
  • Cloning, Molecular
  • DNA, Complementary
  • DNA-Binding Proteins / metabolism
  • Heterogeneous-Nuclear Ribonucleoproteins*
  • Humans
  • Molecular Sequence Data
  • Nucleic Acids / metabolism
  • Poly C / metabolism*
  • RNA-Binding Proteins / genetics*
  • RNA-Binding Proteins / metabolism*
  • Sequence Homology, Amino Acid
  • Transcription Factors*
  • Vaccinia virus / genetics


  • DNA, Complementary
  • DNA-Binding Proteins
  • Heterogeneous-Nuclear Ribonucleoproteins
  • Nucleic Acids
  • PCBP1 protein, human
  • RNA-Binding Proteins
  • Transcription Factors
  • Poly C

Associated data

  • GENBANK/X78136
  • GENBANK/X78137