Dissection of the wheat transcription factor HBP-1a(17) reveals a modular structure for the activation domain.
The wheat bZIP protein HBP-1a(17) is a putative transcription factor regulating histone gene expression. To delineate the functional domain(s) of this factor, we made a series of effector constructs expressing fusion proteins, in which various portions of HBP-1a(17) are fused to the DNA-binding domain of the yeast transcriptional activator GAL4, in plant cells. When the beta-glucuronidase (GUS) reporter gene, driven by the wheat histone H3 core promoter harboring the GAL4-binding sequence, was co-transfected with such effector genes into tobacco protoplasts, several portions of HBP-1a(17) influenced reporter gene expression. The N-terminal one-third of HBP-1a(17), termed the P region (residues 1-118) due to its Pro content, did not activate the reporter gene, in contrast to the corresponding Pro-rich region of Arabidopsis GBF1 (residues 1-110), which functions as an activation domain. When the P region was divided into two, however, both its N-terminal (1-56; termed NP) and C-terminal (58-118; termed PC) halves were able to enhance expression of the reporter gene. When the NP region was further divided into NP(5-30) and NP(30-56), both regions still retained activating ability. These results suggest that the P region of HBP-1a(17) is composed of several modules each having activating function, and modification and/or conformational changes of the P region might influence its function.
Nakayama
T
T
Department of Botany, Graduate School of Science, Kyoto University, Sakyo-ku, Japan.
Okanami
M
M
Meshi
T
T
Iwabuchi
M
M
D017360:Arabidopsis; D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites; D017796:Caulimovirus / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry*; D005656:Fungal Proteins / Q000378:metabolism; D017930:Genes, Reporter; D005966:Glucuronidase / Q000235:genetics; D006657:Histones / Q000235:genetics; D009687:Nuclear Proteins / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000737:chemistry*; D015533:Transcriptional Activation; D014908:Triticum / Q000737:chemistry* / Q000235:genetics
D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; C068756:HBP-1a protein, Triticum aestivum; D006657:Histones; D009687:Nuclear Proteins; D010940:Plant Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D005966:Glucuronidase