Bach proteins belong to a novel family of BTB-basic leucine zipper transcription factors that interact with MafK and regulate transcription through the NF-E2 site.
Members of the small Maf family (MafK, MafF, and MafG) are basic region leucine zipper (bZip) proteins that can function as transcriptional activators or repressors. The dimer compositions of their DNA binding forms determine whether the small Maf family proteins activate or repress transcription. Using a yeast two-hybrid screen with a GAL4-MafK fusion protein, we have identified two novel bZip transcription factors, Bach1 and Bach2, as heterodimerization partners of MafK. In addition to a Cap'n'collar-type bZip domain, these Bach proteins possess a BTB domain which is a protein interaction motif; Bach1 and Bach2 show significant similarity to each other in these regions but are otherwise divergent. Whereas expression of Bach1 appears ubiquitous, that of Bach2 is restricted to monocytes and neuronal cells. Bach proteins bind in vitro to NF-E2 binding sites, recognition elements for the hematopoietic transcription factor NF-E2, by forming heterodimers with MafK. Furthermore, a DNA binding complex that contained MafK as well as Bach2 or a protein related closely to Bach2 was found to be present in mouse brain cells. Bach1 and Bach2 function as transcription repressors in transfection assays using fibroblast cells, but they function as a transcriptional activator and repressor, respectively, in cultured erythroid cells. The results suggest that members of the Bach family play important roles in coordinating transcription activation and repression by MafK.
Department of Biochemistry, Tohoku University School of Medicine, Sendai, Japan.
T
T
Oyake
K
K
Itoh
H
H
Motohashi
N
N
Hayashi
H
H
Hoshino
M
M
Nishizawa
M
M
Yamamoto
K
K
Igarashi
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites; D001921:Brain / Q000378:metabolism*; D003001:Cloning, Molecular; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019281:Dimerization; D050981:Erythroid-Specific DNA-Binding Factors; D016350:Leucine Zippers; D050985:MafK Transcription Factor; D051379:Mice; D008969:Molecular Sequence Data; D009000:Monocytes / Q000378:metabolism; D050983:NF-E2 Transcription Factor; D050984:NF-E2 Transcription Factor, p45 Subunit; D009474:Neurons / Q000378:metabolism*; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic; D016335:Zinc Fingers
C491123:BACH2 protein, human; C486316:Bach1 protein, mouse; C102109:Bach2 protein, mouse; D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D050981:Erythroid-Specific DNA-Binding Factors; D050985:MafK Transcription Factor; C494696:Mafk protein, mouse; D050983:NF-E2 Transcription Factor; D050984:NF-E2 Transcription Factor, p45 Subunit; C494693:Nfe2 protein, mouse; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors