Laboratoire de Pharmacologie Expérimentale et Clinique, Département Cibles Pharmacologiques dans les Cancers, Université Paris 7 Denis Diderot, INSERM U940, 27 rue Juliette Dodu, 75010 Paris, France.
J Exp Clin Cancer Res. 2010 Feb 9;29(1):10. doi: 10.1186/1756-9966-29-10.
SIAH proteins are the human members of an highly conserved family of E3 ubiquitin ligases. Several data suggest that SIAH proteins may have a role in tumor suppression and apoptosis. Previously, we reported that SIAH-1 induces the degradation of Kid (KIF22), a chromokinesin protein implicated in the normal progression of mitosis and meiosis, by the ubiquitin proteasome pathway. In human breast cancer cells stably transfected with SIAH-1, Kid/KIF22 protein level was markedly reduced whereas, the Kid/KIF22 mRNA level was increased. This interaction has been further elucidated through analyzing SIAH and Kid/KIF22 expression in both paired normal and tumor tissues and cell lines. It was observed that SIAH-1 protein is widely expressed in different normal tissues, and in cells lines but showing some differences in western blotting profiles. Immunofluorescence microscopy shows that the intracellular distribution of SIAH-1 and Kid/KIF22 appears to be modified in human tumor tissues compared to normal controls. When mRNA expression of SIAH-1 and Kid/KIF22 was analyzed by real-time PCR in normal and cancer breast tissues from the same patient, a large variation in the number of mRNA copies was detected between the different samples. In most cases, SIAH-1 mRNA is decreased in tumor tissues compared to their normal counterparts. Interestingly, in all breast tumor tissues analyzed, variations in the Kid/KIF22 mRNA levels mirrored those seen with SIAH-1 mRNAs. This concerted variation of SIAH-1 and Kid/KIF22 messengers suggests the existence of an additional level of control than the previously described protein-protein interaction and protein stability regulation. Our observations also underline the need to re-evaluate the results of gene expression obtained by qRT-PCR and relate it to the protein expression and cellular localization when matched normal and tumoral tissues are analyzed.
SIAH 蛋白是一种高度保守的 E3 泛素连接酶家族的人类成员。有几项数据表明，SIAH 蛋白可能在肿瘤抑制和细胞凋亡中发挥作用。之前，我们报道过 SIAH-1 通过泛素蛋白酶体途径诱导染色质运动蛋白 Kid（KIF22）的降解，Kid（KIF22）在有丝分裂和减数分裂的正常进程中起作用。在稳定转染 SIAH-1 的人乳腺癌细胞中，Kid/KIF22 蛋白水平明显降低，而 Kid/KIF22 mRNA 水平升高。通过分析配对的正常和肿瘤组织以及细胞系中的 SIAH 和 Kid/KIF22 表达，进一步阐明了这种相互作用。结果表明，SIAH-1 蛋白在不同的正常组织和细胞系中广泛表达，但在 Western blot 图谱中存在一些差异。免疫荧光显微镜显示，与正常对照相比，SIAH-1 和 Kid/KIF22 的细胞内分布似乎在人肿瘤组织中发生了改变。通过对来自同一患者的正常和癌症乳腺组织中的 SIAH-1 和 Kid/KIF22 的 mRNA 表达进行实时 PCR 分析，在不同样本之间检测到 mRNA 拷贝数的大量变化。在大多数情况下，与正常组织相比，肿瘤组织中的 SIAH-1 mRNA 减少。有趣的是，在所分析的所有乳腺癌组织中，Kid/KIF22 mRNA 水平的变化与 SIAH-1 mRNA 相似。SIAH-1 和 Kid/KIF22 信使的这种协同变化表明，存在比先前描述的蛋白质-蛋白质相互作用和蛋白质稳定性调节更高级别的控制。我们的观察结果还强调，当分析匹配的正常和肿瘤组织时，需要重新评估通过 qRT-PCR 获得的基因表达结果，并将其与蛋白质表达和细胞定位联系起来。
