Dynamic cytoplasmic anchoring of the transcription factor Bach1 by intracellular hyaluronic acid binding protein IHABP.
Bach1 functions as a transcriptional repressor of heme oxygenase-1 (HO-1) and the beta-globin genes. The enhancer regions of these genes contain multiple Maf recognition elements (MAREs) to which Bach1 can bind. Previous studies have shown that increased levels of heme and cadmium induce the nuclear export of Bach1, resulting in cytoplasmic accumulation. By means of a yeast two hybrid screening using Bach1 as bait, we identified the intracellular hyaluronic acid binding protein (IHABP) as a potential regulator of Bach1. IHABP is a microtubule-associated protein that may regulate the organization of the cytoskeletal network. A series of domain analyses revealed that a region of Bach1 previously implicated in cytoplasmic accumulation was necessary for IHABP-binding. A C-terminal region of IHABP was necessary for Bach1-binding. Overexpressed Bach1 colocalized with IHABP in the cytoplasm, forming fiber-like structures on microtubules. Fluorescence recovery after photobleaching (FRAP) analysis revealed a dynamic nature of the Bach1-IHABP interaction in living cells. The repression of HO-1 reporter activity by Bach1 was attenuated by co-transfecting IHABP in a dose-dependent manner. Moreover, the overexpression of IHABP induced the endogenous HO-1 gene in NIH3T3 cells. The overall results suggest that IHABP regulates the subcelluar localization of Bach1 in order to fine-tune transactivation of Bach1 target genes such as HO-1.
Yamasaki
Chikara
C
Department of Biomedical Chemistry, Hiroshima University Graduate School of Biomedical Sciences, Kasumi 1-2-3, Hiroshima 734-8551.
Tashiro
Satoshi
S
Nishito
Yasumasa
Y
Sueda
Taijiro
T
Igarashi
Kazuhiko
K
D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism*; D004794:Enzyme Repression / Q000187:drug effects / Q000502:physiology; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D051856:Fanconi Anemia Complementation Group Proteins; D036681:Fluorescence Recovery After Photobleaching; D006419:Heme Oxygenase (Decyclizing) / Q000096:biosynthesis / Q000235:genetics; D051547:Heme Oxygenase-1; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism; D008565:Membrane Proteins; D051379:Mice; D041681:NIH 3T3 Cells; D014157:Transcription Factors / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
C102108:BACH1 protein, human; D050976:Basic-Leucine Zipper Transcription Factors; D016326:Extracellular Matrix Proteins; D051856:Fanconi Anemia Complementation Group Proteins; D018960:Hyaluronan Receptors; D008565:Membrane Proteins; D014157:Transcription Factors; C098946:hyaluronan-mediated motility receptor; C496541:HMOX1 protein, human; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse