Abstract：
Speckle-type pox virus and zinc finger (POZ) protein (SPOP), a substrate recognition receptor for the cullin-3/RING ubiquitin E3 complex, leads to the ubiquitination of >40 of its target substrates. Since a variety of point mutations in the substrate-binding domain of SPOP have been identified in cancers, including prostate and endometrial cancers, the pathological roles of those cancer-associated SPOP mutants have been extensively elucidated. In this study, we evaluated the cellular functions of wild-type SPOP in non-cancerous human keratinocyte-derived HaCaT cells expressing wild-type SPOP gene. SPOP knockdown using siRNA in HaCaT cells dramatically reduced cell growth and arrested their cell cycles at G1/S phase. The expression of DNA replication licensing factors CDT1 and CDC6 in HaCaT cells drastically decreased on SPOP knockdown as their translation was inhibited. CDT1 and CDC6 downregulation induced p21 expression without p53 activation. Our results suggest that SPOP is essential for DNA replication licensing in non-cancerous keratinocyte HaCaT cells.
摘要：
斑点型痘病毒和锌指（POZ）蛋白（SPOP），cullin-3/RING泛素E3复合物的底物识别受体，导致其>40个目标底物的泛素化。由于已经在癌症中鉴定了SPOP的底物结合域中的各种点突变，包括前列腺癌和子宫内膜癌，这些癌症相关SPOP突变体的病理作用已被广泛阐明.在这项研究中,我们评估了表达野生型SPOP基因的非癌人类角质形成细胞来源的HaCaT细胞中野生型SPOP的细胞功能。在HaCaT细胞中使用siRNA的SPOP敲除显著降低细胞生长并将其细胞周期阻滞在G1/S期。在SPOP敲低时，HaCaT细胞中DNA复制许可因子CDT1和CDC6的表达急剧下降，因为它们的翻译受到抑制。CDT1和CDC6下调诱导p21表达而无p53激活。我们的结果表明，SPOP对于非癌性角质形成细胞HaCaT细胞中的DNA复制许可至关重要。
