Siah-1S, a novel splice variant of Siah-1 (seven in absentia homolog), counteracts Siah-1-mediated downregulation of beta-catenin

作者：Mei Y; Xie C; Xie W; Wu Z; Wu M^*

来源：Oncogene, 2007, 26(43): 6319-6331.

DOI：10.1038/sj.onc.1210449

• Siah-1S
• beta-catenin
• splice variant
• self-ubiquitination
• tumorigenesis

Siah-1 ( seven in absentia homolog) is known to cause indirect degradation of beta-catenin through formation of a complex with Siah-interacting protein ( SIP), Skp1 and Ebi. Here, we report the characterization of a novel splice variant of human Siah-1, designated Siah-1S, which is produced by an alternative splicing mechanism. The novel intron/exon junctions used to generate Siah-1S follow a non-conventional CT-AC rule. Siah-1S exhibits an even shorter half-life than Siah-1 and is able to catalyse self-ubiquitination that results in its subsequent degradation by proteasome. Siah-1S is shown to upregulate beta-catenin-dependent Tcf/Lef transcriptional activation and antagonize Siah-1's potentiation effect on the apoptosis induced by etoposide in MCF-7 cells. Additionally, Siah-1S is found to interact with Siah-1 to form heterodimer or with itself to form homodimer. Unlike homodimer Siah-1*Siah-1, neither Siah-1*Siah-1S nor Siah-1S*Siah-1S is able to bind to Siah-1-interacting protein, which may explain the underlying mechanism for Siah-1S's dominant negative effect on Siah-1. Importantly, results from in vitro soft agar assay demonstrated that Siah-1S displays a promotion effect on cells tumorigenicity.

• 出版日期2007-9-20
• 单位安徽医科大学; 中国科学技术大学