Restelli Michela, Molinari Elisa, Marinari Barbara, Conte Daniele, Gnesutta Nerina, Costanzo Antonio, Merlo Giorgio Roberto, Guerrini Luisa
Department of Biosciences, Università degli Studi di Milano, 20133 Milano, Italy.
Dermatology Unit, NESMOS Department, Università di Roma La Sapienza, I-00189 Rome, Italy and.
Hum Mol Genet. 2015 Aug 1;24(15):4185-97. doi: 10.1093/hmg/ddv151. Epub 2015 Apr 24.
The p63 transcription factor, homolog to the p53 tumor suppressor gene, plays a crucial role in epidermal and limb development, as its mutations are associated to human congenital syndromes characterized by skin, craniofacial and limb defects. While limb and skin-specific p63 transcriptional targets are being discovered, little is known of the post-translation modifications controlling ΔNp63α functions. Here we show that the p300 acetyl-transferase physically interacts in vivo with ΔNp63α and catalyzes its acetylation on lysine 193 (K193) inducing ΔNp63α stabilization and activating specific transcriptional functions. Furthermore we show that Fibroblast Growth Factor-8 (FGF8), a morphogenetic signaling molecule essential for embryonic limb development, increases the binding of ΔNp63α to the tyrosine kinase c-Abl as well as the levels of ΔNp63α acetylation. Notably, the natural mutant ΔNp63α-K193E, associated to the Split-Hand/Foot Malformation-IV syndrome, cannot be acetylated by this pathway. This mutant ΔNp63α protein displays promoter-specific loss of DNA binding activity and consequent altered expression of development-associated ΔNp63α target genes. Our results link FGF8, c-Abl and p300 in a regulatory pathway that controls ΔNp63α protein stability and transcriptional activity. Hence, limb malformation-causing p63 mutations, such as the K193E mutation, are likely to result in aberrant limb development via the combined action of altered protein stability and altered promoter occupancy.
p63转录因子是p53肿瘤抑制基因的同源物，在表皮和肢体发育中起关键作用，因为其突变与以皮肤、颅面和肢体缺陷为特征的人类先天性综合征相关。虽然肢体和皮肤特异性的p63转录靶点正在被发现，但对于控制ΔNp63α功能的翻译后修饰却知之甚少。在这里，我们表明p300乙酰转移酶在体内与ΔNp63α发生物理相互作用，并催化其赖氨酸193（K193）位点的乙酰化，从而诱导ΔNp63α的稳定并激活特定的转录功能。此外，我们还表明，成纤维细胞生长因子8（FGF8）是胚胎肢体发育所必需的形态发生信号分子，它增加了ΔNp63α与酪氨酸激酶c-Abl的结合以及ΔNp63α的乙酰化水平。值得注意的是，与裂手/裂足畸形-IV综合征相关的天然突变体ΔNp63α-K193E不能被该途径乙酰化。这种突变的ΔNp63α蛋白表现出启动子特异性的DNA结合活性丧失，进而导致与发育相关的ΔNp63α靶基因的表达改变。我们的结果将FGF8、c-Abl和p300联系在一个控制ΔNp63α蛋白稳定性和转录活性的调节途径中。因此，导致肢体畸形的p63突变，如K193E突变，可能通过改变蛋白质稳定性和改变启动子占据的联合作用导致异常的肢体发育。
