title: Role of the CCAAT-binding protein NFY in SCA17 pathogenesis.
abstract: Spinocerebellar ataxia 17 (SCA17) is caused by expansion of the polyglutamine (polyQ) tract in human TATA-box binding protein (TBP) that is ubiquitously expressed in both central nervous system and peripheral tissues. The spectrum of SCA17 clinical presentation is broad. The precise pathogenic mechanism in SCA17 remains unclear. Previously proteomics study using a cellular model of SCA17 has revealed reduced expression of heat shock 70 kDa protein 5 (HSPA5) and heat shock 70 kDa protein 8 (HSPA8), suggesting that impaired protein folding may contribute to the cell dysfunction of SCA17 (Lee et al., 2009). In lymphoblastoid cells, HSPA5 and HSPA8 expression levels in cells with mutant TBP were also significantly lower than that of the control cells (Chen et al., 2010). As nuclear transcription factor Y (NFY) has been reported to regulate HSPA5 transcription, we focused on if NFY activity and HSPA5 expression in SCA17 cells are altered. Here, we show that TBP interacts with NFY subunit A (NFYA) in HEK-293 cells and NFYA incorporated into mutant TBP aggregates. In both HEK-293 and SH-SY5Y cells expressing TBP/Q(61~79), the level of soluble NFYA was significantly reduced. In vitro binding assay revealed that the interaction between TBP and NFYA is direct. HSPA5 luciferase reporter assay and endogenous HSPA5 expression analysis in NFYA cDNA and siRNA transfection cells further clarified the important role of NFYA in regulating HSPA5 transcription. In SCA17 cells, HSPA5 promoter activity was activated as a compensatory response before aggregate formation. NFYA dysfunction was indicated in SCA17 cells as HSPA5 promoter activity reduced along with TBP aggregate formation. Because essential roles of HSPA5 in protection from neuronal apoptosis have been shown in a mouse model, NFYA could be a target of mutant TBP in SCA17.
authors.affiliation: Department of Life Science, National Taiwan Normal University, Taipei, Taiwan.
authors.forename: Li-Ching
authors.initials: LC
authors.lastname: Lee
authors.forename: Chiung-Mei
authors.initials: CM
authors.lastname: Chen
authors.forename: Hao-Chun
authors.initials: HC
authors.lastname: Wang
authors.forename: Hsiao-Han
authors.initials: HH
authors.lastname: Hsieh
authors.forename: I-Sheng
authors.initials: IS
authors.lastname: Chiu
authors.forename: Ming-Tsan
authors.initials: MT
authors.lastname: Su
authors.forename: Hsiu-Mei
authors.initials: HM
authors.lastname: Hsieh-Li
authors.forename: Chung-Hsin
authors.initials: CH
authors.lastname: Wu
authors.forename: Guan-Chiun
authors.initials: GC
authors.lastname: Lee
authors.forename: Guey-Jen
authors.initials: GJ
authors.lastname: Lee-Chen
authors.forename: Jung-Yaw
authors.initials: JY
authors.lastname: Lin
mesh_terms: D023081:CCAAT-Binding Factor / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D015870:Gene Expression; D057809:HEK293 Cells; D006360:Heat-Shock Proteins / Q000235:genetics; D006801:Humans; D050505:Mutant Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D021381:Protein Transport; D020754:Spinocerebellar Ataxias / Q000209:etiology*; D035181:TATA-Box Binding Protein / Q000378:metabolism
chemical_list: D023081:CCAAT-Binding Factor; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D050505:Mutant Proteins; C492061:NFYA protein, human; D035181:TATA-Box Binding Protein