title: SIAH-1 interacts with mammalian polyhomeotic homologues HPH2 and affects its stability via the ubiquitin-proteasome pathway.
abstract: Polycomb Group (PcG) genes encode proteins that form large multimeric and chromatin-associated complexes implicated in the stable repression of developmentally essential genes. HPH2, the Homo sapiens polyhomeotic homologue 2, functions as one of the subunits of PcG complex 1. In our study, SIAH-1, an E3 ligase, could directly associate with HPH2 both in vitro and in vivo. Both the cysteine-rich region of SIAH-1 and the PxVxAxP motif of HPH2 were essential for the interaction. HPH2 was co-localized with SIAH-1 in nuclei. Furthermore, SIAH-1 was able to facilitate the ubiquitination and degradation of HPH2 via ubiquitin-proteasome pathway in vivo. The ubiquitination activity was severely impaired in the SIAH-1 mutant that either lost E3 ligase activity or had weakened binding ability with HPH2, strongly suggesting that SIAH-1 was the direct E3 ligase of HPH2. Thus, our results propose a novel role of SIAH-1 in regulating the expression level of HPH2 through the ubiquitin-proteasome pathway.
authors.affiliation: State Key Laboratory of Genetic Engineering, Institute of Genetics, School of Life Sciences, Fudan University, 220 Handan Rd., Shanghai 200433, PR China.
authors.forename: Huiling
authors.initials: H
authors.lastname: Wu
authors.forename: Ying
authors.initials: Y
authors.lastname: Lin
authors.forename: Yan
authors.initials: Y
authors.lastname: Shi
authors.forename: Wei
authors.initials: W
authors.lastname: Qian
authors.forename: Zhipeng
authors.initials: Z
authors.lastname: Tian
authors.forename: Yao
authors.initials: Y
authors.lastname: Yu
authors.forename: Keke
authors.initials: K
authors.lastname: Huo
mesh_terms: D002460:Cell Line; D006367:HeLa Cells; D006801:Humans; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D063151:Polycomb Repressive Complex 2; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D055550:Protein Stability; D014157:Transcription Factors / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination; D000098563:Seven in Absentia Proteins
chemical_list: D009687:Nuclear Proteins; C485977:PHC2 protein, human; D014157:Transcription Factors; D025801:Ubiquitin; D063151:Polycomb Repressive Complex 2; D044767:Ubiquitin-Protein Ligases; D000098563:Seven in Absentia Proteins; D046988:Proteasome Endopeptidase Complex