The nuclear PP1 interacting protein ZAP3 (ZAP) is a putative nucleoside kinase that complexes with SAM68, CIA, NF110/45, and HNRNP-G

Biochim Biophys Acta. 2007 Oct;1774(10):1339-50. doi: 10.1016/j.bbapap.2007.07.015. Epub 2007 Aug 15.


The targeting of protein kinases and phosphatases is fundamental to their roles as cellular regulators. The type one serine/threonine protein phosphatase (PP1) is enriched in the nucleus, yet few nuclear PP1 targeting subunits have been described and characterized. Here we show that the human protein, ZAP3 (also known as ZAP), is localized to the nucleus, that it is expressed in all mammalian tissues examined, and docks to PP1 through an RVRW motif located in its highly conserved carboxy-terminus. Proteomic analysis of a ZAP3 complex revealed that in addition to binding PP1, ZAP3 complexes with CIA (or nuclear receptor co-activator 5) and the RNA binding proteins hnRNP-G, SAM68 and NF110/45, but loses affinity for SAM68 and hnRNP-G upon digestion of endogenous nucleic acid. Bioinformatics has revealed that the conserved carboxy-terminus is orthologous to T4- and mammalian polynucleotide kinases with residues necessary for kinase activity maintained throughout evolution. Furthermore, the substrate binding pocket of uridine-cytidine kinase (or uridine kinase) has localized sequence similarity with ZAP3, suggesting uridine or cytidine as possible ZAP3 substrates. Most polynucleotide kinases have a phosphohydrolase domain in conjunction with their kinase domain. In ZAP3, although this domain is present, it now appears degenerate and functions to bind PP1 through an RVRW docking site located within the domain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism*
  • Amino Acid Motifs / genetics
  • Amino Acid Sequence
  • Animals
  • Binding Sites / genetics
  • Cell Cycle Proteins / metabolism*
  • Conserved Sequence / genetics
  • DNA-Binding Proteins / metabolism*
  • HeLa Cells
  • Heterogeneous-Nuclear Ribonucleoprotein Group F-H / metabolism*
  • Humans
  • Molecular Chaperones
  • Molecular Sequence Data
  • Nuclear Factor 45 Protein / metabolism*
  • Nuclear Factor 90 Proteins / metabolism*
  • Nuclear Proteins / chemistry
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Nucleoproteins / genetics
  • Nucleoproteins / metabolism*
  • Phosphotransferases (Alcohol Group Acceptor) / chemistry
  • Phosphotransferases (Alcohol Group Acceptor) / genetics
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • Phosphotransferases / metabolism*
  • Protein Binding / genetics
  • Protein Phosphatase 1 / chemistry
  • Protein Phosphatase 1 / metabolism*
  • Protein Subunits / chemistry
  • Protein Subunits / metabolism
  • RNA-Binding Proteins / metabolism*
  • Rabbits
  • Rats
  • Repressor Proteins


  • ASF1A protein, human
  • Adaptor Proteins, Signal Transducing
  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • Heterogeneous-Nuclear Ribonucleoprotein Group F-H
  • ILF3 protein, human
  • KHDRBS1 protein, human
  • Molecular Chaperones
  • Nuclear Factor 45 Protein
  • Nuclear Factor 90 Proteins
  • Nuclear Proteins
  • Nucleoproteins
  • Protein Subunits
  • RNA-Binding Proteins
  • Repressor Proteins
  • YLPM1 protein, human
  • Phosphotransferases
  • Phosphotransferases (Alcohol Group Acceptor)
  • nucleoside phosphotransferase
  • Protein Phosphatase 1