Romano Rose-Anne, Birkaya Barbara, Sinha Satrajit
Department of Biochemistry, State University of New York at Buffalo, Buffalo, New York, USA.
J Invest Dermatol. 2006 Jul;126(7):1469-79. doi: 10.1038/sj.jid.5700297. Epub 2006 Apr 27.
p63, a homolog of the tumor suppressor p53, plays an important role in the formation of stratified epithelium such as those in the epidermis of the skin. The p63 gene gives rise to multiple functionally distinct protein isoforms, including the DeltaNp63 class of isoforms, which lacks the N-terminal transactivation domain and is synthesized from an internal promoter. DeltaNp63 proteins are the predominant isoforms expressed in keratinocytes and are thought to be important for maintenance of the proliferative capacity of these cells. Here, we have examined the transcriptional control mechanisms that govern the expression DeltaNp63 in keratinocytes. We first performed DNase I hypersensitive site mapping and demonstrated that the promoter region of DeltaNp63 is in open chromatin state in keratinocytes. To identify the cis-elements that regulate DeltaNp63, we have performed transient transfection assays in keratinocytes with several DeltaNp63 promoter constructs. This identified a short evolutionarily conserved fragment that harbors most of the transcriptional activity of the DeltaNp63 promoter. Biochemical studies of this element have revealed critical roles for CCAAT-box-binding factor (CBF/NF-Y) and Sp1/Sp3 family of proteins. In addition, our data suggest that DeltaNp63 is recruited to and can activate its own promoter, possibly through protein-protein interactions, thus providing an auto-regulatory loop of self-regulation. These studies support the notion that unique and distinct pathways control the expression of individual p53 family members and their various isoforms.
p63是肿瘤抑制因子p53的同源物，在复层上皮的形成中发挥重要作用，如皮肤表皮中的复层上皮。p63基因产生多种功能不同的蛋白质异构体，包括DeltaNp63类异构体，其缺乏N端反式激活结构域，由内部启动子合成。DeltaNp63蛋白是角质形成细胞中表达的主要异构体，被认为对维持这些细胞的增殖能力很重要。在此，我们研究了调控角质形成细胞中DeltaNp63表达的转录控制机制。我们首先进行了DNase I超敏感位点作图，并证明DeltaNp63的启动子区域在角质形成细胞中处于开放染色质状态。为了鉴定调控DeltaNp63的顺式元件，我们用几种DeltaNp63启动子构建体在角质形成细胞中进行了瞬时转染试验。这确定了一个短的进化保守片段，该片段具有DeltaNp63启动子的大部分转录活性。对该元件的生化研究揭示了CCAAT盒结合因子（CBF/NF-Y）和Sp1/Sp3蛋白家族的关键作用。此外，我们的数据表明，DeltaNp63可能通过蛋白质-蛋白质相互作用被招募到其自身启动子并激活它，从而提供一个自我调节的自调控环。这些研究支持了这样一种观点，即独特且不同的途径控制着各个p53家族成员及其各种异构体的表达。
