Differential altered stability and transcriptional activity of ΔNp63 mutants in distinct ectodermal dysplasias
Differential altered stability and transcriptional activity of ΔNp63 mutants in distinct ectodermal dysplasias
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DOI：
10.1242/jcs.079327
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发表时间：
2011-07-01
影响因子：
4
通讯作者：
Melino, Gerry
中科院分区：
文献类型：
--
作者：
Browne, Gareth;Cipollone, Rita;Melino, Gerry
P63是上皮发育中的关键转录因子，它的杂合突变是导致多种人类外胚层发育不良疾病的原因。虽然这些疾病的突变谱显示出显著的基因型-表型关联，但这种关联的分子基础仅是表面上的已知。在这里，我们研究了Delta Np63突变体(即缺乏N-末端反式激活结构域的p63异构体的突变体)的转录活性和蛋白质稳定性，这些突变体在指-外胚层发育不良-裂隙综合征(EEC)、强直性眼球-外胚层发育不良-裂隙综合征(AEC)和非综合征性裂手/裂足畸形(SHFM)中被发现。DNA结合和无菌α基序(SAM)结构域突变分别在EEC和AEC综合征患者的皮肤中积累，并在体外显示延长的半衰期。相比之下，在SHFM患者中发现的C末端突变的半衰期与野生型蛋白相似。野生型Delta Np63的过表达逆转了EEC和AEC突变蛋白延长的半衰期。有趣的是，突变蛋白表现出与E3泛素连接酶Itch的正常结合和降解。最后，EEC和AEC突变蛋白在几个皮肤特异性基因启动子上的转录活性降低，而SHFM突变蛋白在转录活性上是活跃的。因此，我们的结果为p63的调控反馈机制提供了证据，该机制通过一种未知的机制将转录活性与蛋白质稳态的调控联系起来。这种调控机制的破坏可能是导致p63相关发育障碍的原因之一。
Heterozygous mutations of p63, a key transcription factor in epithelial development, are causative in a variety of human ectodermal dysplasia disorders. Although the mutation spectrum of these disorders displays a striking genotype-phenotype association, the molecular basis for this association is only superficially known. Here, we characterize the transcriptional activity and protein stability of Delta Np63 mutants (that is, mutants of a p63 isoform that lacks the N-terminal transactivation domain) that are found in ectrodactyly-ectodermal dysplasia-cleft syndrome (EEC), ankyloblepharon-ectodermal dysplasia-clefting syndrome (AEC) and nonsyndromic split-hand/split-foot malformation (SHFM). DNA-binding and sterile alpha motif (SAM) domain mutants accumulate in the skin of EEC and AEC syndrome patients, respectively, and show extended half lives in vitro. By contrast, C-terminal mutations found in SHFM patients have half-lives similar to that of the wild-type protein. The increased half-life of EEC and AEC mutant proteins was reverted by overexpression of wild-type Delta Np63. Interestingly, the mutant proteins exhibit normal binding to and degradation by the E3 ubiquitin ligase Itch. Finally, EEC and AEC mutant proteins have reduced transcriptional activity on several skin-specific gene promoters, whereas SHFM mutant proteins are transcriptionally active. Our results, therefore, provide evidence for a regulatory feedback mechanism for p63 that links transcriptional activity to regulation of protein homeostasis by an unknown mechanism. Disruption of this regulatory mechanism might contribute to the pathology of p63-related developmental disorders.