FOX-2 Dependent Splicing of Ataxin-2 Transcript Is Affected by Ataxin-1 Overexpression

Abstract

Alternative splicing is a fundamental posttranscriptional mechanism for controlling gene expression, and splicing defects have been linked to various human disorders. The splicing factor FOX-2 is part of a main protein interaction hub in a network related to human inherited ataxias, however, its impact remains to be elucidated. Here, we focused on the reported interaction between FOX-2 and ataxin-1, the disease-causing protein in spinocerebellar ataxia type 1. In this line, we further evaluated this interaction by yeast-2-hybrid analyses and co-immunoprecipitation experiments in mammalian cells. Interestingly, we discovered that FOX-2 localization and splicing activity is affected in the presence of nuclear ataxin-1 inclusions. Moreover, we observed that FOX-2 directly interacts with ataxin-2, a protein modulating spinocerebellar ataxia type 1 pathogenesis. Finally, we provide evidence that splicing of pre-mRNA of ataxin-2 depends on FOX-2 activity, since reduction of FOX-2 levels led to increased skipping of exon 18 in ataxin-2 transcripts. Most striking, we observed that ataxin-1 overexpression has an effect on this splicing event as well. Thus, our results demonstrate that FOX-2 is involved in splicing of ataxin-2 transcripts and that this splicing event is altered by overexpression of ataxin-1.

Proteins Containing Expanded Polyglutamine Tracts and Neurodegenerative Disease

“…186 The AXH domain and the nuclear localization signal in ataxin-1 are involved in inclusion formation. 187–190 The AXH domain itself has a propensity to aggregate and may be involved in initiating fibrilization. 189, 191, 192 The pathogenic threshold length associated with some polyQ diseases appears dependent on the polarity of its flanking sequence.…”

Kaleidoscopic protein–protein interactions in the life and death of ataxin-1: new strategies against protein aggregation

“…In the case of RBM17 and U2AF65, the interaction was mapped onto the short linear UHM ligand motif (ULM) in the C terminus of Atx1, a sequence known to be involved in recognition of the splicing factor U2AF (U2 auxiliary factor) homology motif (UHM) domain [20]. It was also shown that Atx1 has a positive effect on U2AF65 splicing [20] and that overexpression of Atx1 positively affects splicing of transcripts of the other polyQ-containing protein ataxin-2 by RBM9/FOX2 [42]. These findings strongly suggest a specific role of Atx1 in pre-mRNA processing.…”

New alternative splicing variants of the ATXN2 transcript

“…The splice variants were named type II in which exon 10 is lacking (present in human and mouse cDNAs) [39], type III lacking exon 10 and exon 11 (only seen in mouse) [39,40] and type IV deficient in exon 21 [41]. Importantly, the alternative splicing of Ataxin-2 in neurons is under control of RBFOX2 and to be modulated by the SCA1 disease protein Ataxin-1 [42], while in oligodendroglial cells it is controlled by Quaking [43].…”