Romano Rose-Anne, Ortt Kori, Birkaya Barbara, Smalley Kirsten, Sinha Satrajit
Department of Biochemistry, State University of New York at Buffalo, Center for Excellence in Bioinformatics and Life Sciences, Buffalo, New York, USA.
PLoS One. 2009 May 20;4(5):e5623. doi: 10.1371/journal.pone.0005623.
One major defining characteristic of the basal keratinocytes of the stratified epithelium is the expression of the keratin genes K5 and K14. The temporal and spatial expression of these two genes is usually tightly and coordinately regulated at the transcriptional level. This ensures the obligate pairing of K5 and K14 proteins to generate an intermediate filament (IF) network that is essential for the structure and function of the proliferative keratinocytes. Our previous studies have shown that the basal-keratinocyte restricted transcription factor p63 is a direct regulator of K14 gene.
METHODOLOGY/PRINCIPAL FINDINGS: Here we provide evidence that p63, specifically the DeltaN isoform also regulates the expression of the K5 gene by binding to a conserved enhancer within the 5' upstream region. By using specific antibodies against DeltaNp63, we show a concordance in the expression between basal keratins and DeltaNp63 proteins but not the TAp63 isoforms during early embryonic skin development. We demonstrate, that contrary to a previous report, transgenic mice expressing DeltaNp63 in lung epithelium exhibit squamous metaplasia with de novo induction of K5 and K14 as well as transdifferentiation to the epidermal cell lineage. Interestingly, the in vivo epidermal inductive properties of DeltaNp63 do not require the C-terminal SAM domain. Finally, we show that DeltaNp63 alone can restore the expression of the basal keratins and reinitiate the failed epidermal differentiation program in the skin of p63 null animals.
DeltaNp63 is a critical mediator of keratinocyte stratification program and directly regulates the basal keratin genes.
复层上皮基底角质形成细胞的一个主要特征是角蛋白基因K5和K14的表达。这两个基因的时空表达通常在转录水平受到紧密且协调的调控。这确保了K5和K14蛋白的必然配对以形成中间丝（IF）网络，该网络对于增殖性角质形成细胞的结构和功能至关重要。我们之前的研究表明，基底角质形成细胞特异性转录因子p63是K14基因的直接调节因子。
方法/主要发现：在此我们提供证据表明，p63，特别是DeltaN异构体，也通过结合5'上游区域内的一个保守增强子来调节K5基因的表达。通过使用针对DeltaNp63的特异性抗体，我们发现在胚胎早期皮肤发育过程中，基底角蛋白和DeltaNp63蛋白之间的表达具有一致性，但TAp63异构体之间则不然。我们证明，与之前的一份报告相反，在肺上皮中表达DeltaNp63的转基因小鼠表现出鳞状化生，伴有K5和K14的从头诱导以及向表皮细胞谱系的转分化。有趣的是，DeltaNp63的体内表皮诱导特性不需要C末端SAM结构域。最后，我们表明单独的DeltaNp63可以恢复基底角蛋白的表达，并重新启动p63基因敲除动物皮肤中失败的表皮分化程序。
DeltaNp63是角质形成细胞分层程序的关键介质，并直接调节基底角蛋白基因。
