Conserved Ser residues in the basic region of the bZIP-type transcription factor HBP-1a(17): importance in DNA binding and possible targets for phosphorylation

Plant Mol Biol. 1998 Jan;36(1):125-36. doi: 10.1023/a:1005934332530.

Abstract

HBP-1a(17) is representative of a group of plant bZIP-type transcription factors which includes HBP-1a proteins and G-box-binding factors. We found kinase activity in wheat nuclear extract that phosphorylated HBP-1a(17). Experiments using recombinant HBP-1a(17) derivatives as substrates revealed that all three of the Ser residues in the basic region, Ser-261, Ser-265, and Ser-269, were phosphorylated in a Ca(2+)-stimulated manner. DNA-binding analysis of mutants with a Ser-to-Glu change, prepared to mimic the phosphorylated proteins, indicated that introduction of a negative charge at position 265 or 269 prevents HBP-1a(17) from binding DNA not only in the homodimer of mutants but also in heterodimers with a wild-type protein. It is therefore suggested that the phosphorylation regulates the function of HBP-1a(17) at least at the level of DNA binding. Since Ser-265 and Ser-269 are highly conserved among the plant bZIP-type factors known to date, a common Ca(2+)-mediated regulatory mechanism may exert an effect on the bZIP-type factors through phosphorylation of these conserved Ser residues.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Basic-Leucine Zipper Transcription Factors
  • Binding Sites
  • Calcium / pharmacology
  • Cell Nucleus / metabolism
  • Cells, Cultured
  • Cloning, Molecular
  • Conserved Sequence
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / isolation & purification
  • DNA-Binding Proteins / metabolism*
  • Leucine Zippers
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Nuclear Proteins / chemistry
  • Nuclear Proteins / isolation & purification
  • Nuclear Proteins / metabolism*
  • Peptide Mapping
  • Phosphopeptides / chemistry
  • Phosphorylation
  • Phosphoserine / metabolism
  • Plant Proteins / metabolism
  • Point Mutation
  • Polymerase Chain Reaction
  • Recombinant Fusion Proteins / biosynthesis
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • Restriction Mapping
  • Saccharomyces cerevisiae
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Serine
  • Transcription Factors / chemistry
  • Transcription Factors / isolation & purification
  • Transcription Factors / metabolism*
  • Triticum / metabolism*
  • beta-Galactosidase / biosynthesis

Substances

  • Basic-Leucine Zipper Transcription Factors
  • DNA-Binding Proteins
  • HBP-1a protein, Triticum aestivum
  • Nuclear Proteins
  • Phosphopeptides
  • Plant Proteins
  • Recombinant Fusion Proteins
  • Recombinant Proteins
  • Transcription Factors
  • Phosphoserine
  • Serine
  • beta-Galactosidase
  • Calcium