Interaction between PHOX2B and CREBBP mediates synergistic activation: mechanistic implications of PHOX2B mutants.
Congenital central hypoventilation syndrome (CCHS) is a disorder of the autonomic nervous system. The genetic defect is usually caused by heterozygous mutations of the PHOX2B gene such as a 20-alanine tract (+5 to+13 alanines) expansion (approximately 95%) and occasional frameshift or missense mutations. Cytoplasmic aggregates were shown in PHOX2B proteins with longer alanine tract (+9 and longer) expansion and impaired DNA binding was observed in PHOX2B proteins with frameshift, missense, or longer alanine tract (+9 and longer) expansion. Defective transactivation activity was shown in certain PHOX2B mutants. However, PHOX2B proteins with short alanine tract (+5 to+7) expansion in the majority of patients (approximately 75%) did not have cytoplasmic aggregates or DNA binding defects. CREB-binding protein (CREBBP/CBP) is a transcriptional coactivator that interacts with multiple transcription factors to cause synergistic activation. Here we show that CBP interacted with PHOX2B and served as its coactivator to mediate synergistic activation. Wild-type PHOX2B and CBP used specific domains to interact with each other. The domains of CBP that interacted with different PHOX2B mutants were different compared to those interacting with wild-type PHOX2B. Transient cotransfection assays using different PHOX2B mutants and CBP showed the impaired synergistic activation caused by different PHOX2B mutants. An interfering effect was observed in certain PHOX2B mutants. These results demonstrated that aberrant interaction of PHOX2B mutants with CBP and/or an interfering effect of certain PHOX2B mutants may be the critical mechanism to impair synergistic activation, thereby contributing to the phenotypes of CCHS.
Wu
Han-Tsang
HT
Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, Taiwan.
Su
Yi-Ning
YN
Hung
Chia-Cheng
CC
Hsieh
Wu-Shiun
WS
Wu
Kou-Juey
KJ
D015153:Blotting, Western; D050882:CREB-Binding Protein / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004299:Dopamine beta-Hydroxylase / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007040:Hypoventilation / Q000151:congenital / Q000235:genetics; D047468:Immunoprecipitation; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013577:Syndrome; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
D018398:Homeodomain Proteins; C109220:NBPhox protein; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D008156:Luciferases; D004299:Dopamine beta-Hydroxylase; D050882:CREB-Binding Protein; C494363:CREBBP protein, human