title: Differential altered stability and transcriptional activity of ΔNp63 mutants in distinct ectodermal dysplasias.
abstract: 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 ΔNp63 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 ΔNp63. 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.
authors.affiliation: Medical Research Council, Leicester University, Leicester LE19HN, UK.
authors.forename: Gareth
authors.initials: G
authors.lastname: Browne
authors.forename: Rita
authors.initials: R
authors.lastname: Cipollone
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Lena
authors.forename: Valeria
authors.initials: V
authors.lastname: Serra
authors.forename: Huiqing
authors.initials: H
authors.lastname: Zhou
authors.forename: Hans
authors.initials: H
authors.lastname: van Bokhoven
authors.forename: Volker
authors.initials: V
authors.lastname: Dötsch
authors.forename: Daniele
authors.initials: D
authors.lastname: Merico
authors.forename: Roberto
authors.initials: R
authors.lastname: Mantovani
authors.forename: Alessandro
authors.initials: A
authors.lastname: Terrinoni
authors.forename: Richard A
authors.initials: RA
authors.lastname: Knight
authors.forename: Eleonora
authors.initials: E
authors.lastname: Candi
authors.forename: Gerry
authors.initials: G
authors.lastname: Melino
mesh_terms: D002971:Cleft Lip / Q000235:genetics; D002972:Cleft Palate / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004476:Ectodermal Dysplasia / Q000235:genetics*; D005124:Eye Abnormalities / Q000235:genetics; D005143:Eyelids / Q000002:abnormalities; D040181:Genetic Diseases, X-Linked / Q000235:genetics; D057809:HEK293 Cells; D006207:Half-Life; D006801:Humans; D017880:Limb Deformities, Congenital / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D055550:Protein Stability; D011973:Receptors, LDL / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D015533:Transcriptional Activation / Q000235:genetics*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: C081876:CKAP4 protein, human; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D020033:Protein Isoforms; D011973:Receptors, LDL; D012097:Repressor Proteins; C506800:SAMD1 protein, human; C432966:ITCH protein, human; D044767:Ubiquitin-Protein Ligases