Poster abstracts
Poster number 81 submitted by Justin Mabin
Diversity and plasticity of human spliceosomal small nuclear RNA variants
Justin W. Mabin (Biomolecular Chemistry, University of Wisconsin-Madison), Katherine Senn (Biomolecular Chemistry, University of Wisconsin-Madison), Heidi Dvinge (Biomolecular Chemistry, University of Wisconsin-Madison)
Abstract:
Splicing is a highly dynamic and regulated process that shapes the human transcriptome. To date, much of the research on splicing regulation has focused on auxiliary splicing factors. But, increasing evidence has shown that core-splicing proteins are also involved in regulating transcript-specific splicing events (1,2). In addition, the spliceosome contains five small nuclear RNAs (snRNAs) that are responsible for carrying out much of the splicing reaction. snRNAs are loaded with their own complement of proteins forming small nuclear ribonucleoprotein (snRNP) complexes that function in splice site recognition, spliceosome assembly and splicing catalysis. Recently, it has been shown that snRNP proteins are differentially expressed across human tissues, hinting at a cell-type specific regulatory role of core snRNP proteins (3). Recent work has also shown that snRNAs are expressed in a cell-type specific manner in humans, and the relative abundance of snRNAs has been implicated in establishing cellular splicing programs (4). In addition, the human genome has over 1,600 annotated snRNA sequence variant genes. However, due to their numerous insertions, deletions and base changes, many of these variants have been given the label of pseudogenes as they are supposedly not expressed. But, it has been found that some snRNA sequence variants are expressed in human cells (5,6), and may play a role in regulating cellular differentiation (7). Yet, it is not known how many snRNA sequence variants are expressed in humans and if they can form functional snRNPs. In order to determine which snRNA sequence variants are expressed and potentially functional, we have analyzed human tissue and pooled cell lines for the expression of over eighty snRNA sequence variants. This data shows that many more snRNA gene variants are actually expressed in human cells than had originally been appreciated. Intriguingly, we have found that a subset of these expressed sequence variants are not able to form snRNPs. This indicates that expression does not necessarily correlate with snRNP function. However, we have also identified a number of novel variants that are able to incorporating into spliceosomes. It remains unknown how these variants impact cellular splicing, as snRNA variants themselves have remain largely uncharacterized.
References:
1. Papasaikas et. al. (2015) Functional splicing network reveals extensive regulatory potential of the core spliceosomal machinery. Molecular Cell
2. Saltzman et. al. (2011) Regulation of alternative splicing by the core spliceosomal machinery. Genes Dev.
3. Grosso et. al. (2008) Tissue-specific splicing factor gene expression signatures. Nucleic Acid Res.
4. Dvinge et. al. (2018) RNA components of the spliceosome regulate tissue- and cancers-specific alternative splicing. bioRxiv
5. O’Reilly et. al. (2013) Differentially expressed, variant U1 snRNAs regulate gene expression in human cells. Genome Res.
6. Sontheimer EJ and Steitz JA (1992) Three novel functional variants of human U5 small nuclear RNA. Mol Cell Biol.
7. Vazquez-Arango P and O’Reilly D (2017) Variant snRNPs: new players within the spliceosome system. RNA Biol.
Keywords: snRNAs, variant snRNPs, pre-mRNA splicing