The HBP-1 family of wheat basic/leucine zipper proteins interacts with overlapping cis-acting hexamer motifs of plant histone genes.
The type I element (CCACGTCANCGATCCGCG) is a cis-acting element that is essential for the transcriptional regulation of the wheat histone H3 (TH012) gene. The sequence CCACGTCA in the type I element resembles various plant regulatory elements that share an ACGT core sequence, which can be recognized by different basic/leucine zipper (bZIP) proteins. Here we describe the isolation and characterization of wheat cDNA clones encoding three novel bZIP proteins, designated HBP (histone promoter-binding protein)-1a(1), HBP-1a(c14), and HBP-1b(c1). These proteins specifically bind to the ACGT core sequence and, together with previously identified HBP-1a(17) and HBP-1b(c38), constitute a protein family, named the HBP-1 family. Based on their structural characteristics and DNA binding specificities, members of the HBP-1 family can be grouped into HBP-1a and HBP-1b subfamilies. The HBP-1a isoforms are characterized by their N-terminal proline-rich domain and a C-terminal bZIP domain, which binds to the CCACGT motif. In contrast, the HBP-1b isoforms have a bZIP domain at the N terminus, which binds to the ACGTCA motif, and a glutamine-rich domain at the C terminus. All members of both subfamilies interact with the CCACGTCA sequence, but their DNA binding specificities and affinities differ. Since HBP-1a isoforms form heterodimers in all pairwise combinations, heterodimer formation among these bZIP proteins may generate an expanded repertoire of regulatory potential for gene expression in plants.
Mikami
K
K
Division of Developmental Biology, National Institute for Basic Biology, Okazaki, Japan.
Sakamoto
A
A
Iwabuchi
M
M
D000595:Amino Acid Sequence; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites; D001667:Binding, Competitive; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli; D051790:G-Box Binding Factors; D005786:Gene Expression Regulation; D017343:Genes, Plant; D006657:Histones / Q000235:genetics*; D016350:Leucine Zippers / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D009838:Oligodeoxyribonucleotides / Q000378:metabolism / Q000494:pharmacology; D010957:Plasmids; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors; D014908:Triticum / Q000235:genetics* / Q000378:metabolism*
D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D051790:G-Box Binding Factors; D006657:Histones; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D014157:Transcription Factors; C062189:histone DNA binding protein-1; D004247:DNA