Two new p73 splice variants, gamma and delta, with different transcriptional activity.
Two new p73 splice variants, gamma and delta, with different transcriptional activity.
复制标题
具有不同转录活性的两个新的P73剪接变体伽马和三角洲。
DOI：
10.1084/jem.188.9.1763
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发表时间：
1998-11-02
影响因子：
15.3
通讯作者：
Melino, G
中科院分区：
文献类型：
--
作者：
De Laurenzi, V;Costanzo, A;Barcaroli, D;Terrinoni, A;Falco, M;Annicchiarico-Petruzzelli, M;Levrero, M;Melino, G
p73 最近被鉴定为转录因子 p53 的新结构和功能同源物。它以全长形式 α 或较短的 β mRNA 变体（外显子 13 被剪接）表达。在这里，我们报告了两种新的 p73 剪接变体 γ（剪接外显子 11）和 δ（剪接外显子 11、12 和 13）的鉴定和功能表征。 γ 和 δ p73 变体均在人外周血淋巴细胞、原代角质形成细胞和不同肿瘤细胞系（包括神经母细胞瘤、胶质母细胞瘤、黑色素瘤、肝癌和白血病）中表达。四种 p73 剪接变体的表达模式在不同谱系的原代细胞和建立的细胞系中甚至在同一类型的肿瘤内也不同。使用双杂交测定来表征 p73 变体之间的同二聚体和异二聚体相互作用，结果表明 p73γ 和 p73δ 均不与 p53 相互作用，而 p73γ 与所有 p73 异构体均表现出强烈的相互作用，并且 p73δ 有效结合 p73α 和 p73γ，但仅与 p73β 结合较弱。在功能水平上，p73γ激活p21Waf1/Cip1启动子转录的效率明显低于p53或p73β，而p73δ的作用处于中等水平，与p73α相当。不同 p73 变体影响 p53 缺失骨肉瘤 SAOS-2 细胞生长的能力与其 p21Waf1/Cip1 启动子上的转录活性相关：p73β 在抑制集落形成方面最有效，而 p73γ 几乎无效。我们的结果表明，p73 亚型可能受到差异性调节，四种不同的亚型能够在它们之间以及与 p53 相互作用。每个剪接变体的相对表达水平可能通过影响异二聚体形成来调节 p73 转录和生长抑制活性。
p73 has been recently identified as a new structural and functional homologue of the transcription factor p53. It is expressed in either a full-length form, α, or a shorter β mRNA variant, with exon 13 spliced out. Here we report the identification and functional characterization of two new p73 splicing variants, γ (splicing out exon 11) and δ (splicing out exons 11, 12, and 13). Both γ and δ p73 variants are expressed in human peripheral blood lymphocytes, primary keratinocytes, and different tumor cell lines, including neuroblastoma, glioblastoma, melanoma, hepatoma, and leukemia. The expression pattern of the four p73 splicing variants differs in both primary cells of different lineage and established cell lines even within the same type of tumor. A two-hybrid assay was used to characterize the homodimeric and heterodimeric interactions between the p73 variants, and showed that neither p73γ nor p73δ interact with p53, whereas p73γ showed strong interactions with all p73 isoforms, and p73δ binds efficiently p73α and p73γ but only weakly p73β. At the functional level, p73γ is significantly less efficient in activating transcription of the p21Waf1/Cip1 promoter than p53 or p73β, whereas the effect of p73δ is intermediate and comparable to that of p73α. The ability of the different p73 variants to affect cell growth in p53 null osteosarcoma SAOS-2 cells correlates with their transcriptional activity on the p21Waf1/Cip1 promoter: p73β is the most efficient in inhibiting colony formation, whereas p73γ is almost ineffective. Our results suggest that p73 isoforms may be differentially regulated, with four different isoforms capable of interacting among themselves and with p53. The relative expression level of each splice variant may modulate p73 transcriptional and growth suppression activities by affecting heterodimer formation.