Acceptor splice site recognition (3' splice site: 3'ss) is a fundamental step in precursor messenger RNA (pre-mRNA) splicing. Generally, the U2 small nuclear ribonucleoprotein (snRNP) auxiliary factor (U2AF) heterodimer recognizes the 3'ss, of which U2AF35 has a dual function: (i) It binds to the intron-exon border of some 3'ss and (ii) mediates enhancer-binding splicing activators' interactions with the spliceosome. Alternative mechanisms for 3'ss recognition have been suggested, yet they are still not thoroughly understood. Here, we analyzed 3'ss recognition where the intron-exon border is bound by a ubiquitous splicing regulator SRSF1. Using the minigene analysis of two model exons and their mutants, BRCA2 exon 12 and VARS2 exon 17, we showed that the exon inclusion correlated much better with the predicted SRSF1 affinity than 3'ss quality, which were assessed using the Catalog of Inferred Sequence Binding Preferences of RNA binding proteins (CISBP-RNA) database and maximum entropy algorithm (MaxEnt) predictor and the U2AF35 consensus matrix, respectively. RNA affinity purification proved SRSF1 binding to the model 3'ss. On the other hand, knockdown experiments revealed that U2AF35 also plays a role in these exons' inclusion. Most probably, both factors stochastically bind the 3'ss, supporting exon recognition, more apparently in VARS2 exon 17. Identifying splicing activators as 3'ss recognition factors is crucial for both a basic understanding of splicing regulation and human genetic diagnostics when assessing variants' effects on splicing.

• Klíčová slova
• SRSF1, U2AF35, acceptor splice site recognition, pre-mRNA splicing, splicing enhancer,
• MeSH
• alternativní sestřih genetika   MeSH
• exony genetika   MeSH
• HeLa buňky MeSH
• introny genetika   MeSH
• lidé MeSH
• místa sestřihu RNA genetika   fyziologie   MeSH
• proteiny vázající RNA metabolismus   MeSH
• regulační oblasti nukleových kyselin genetika   MeSH
• sekvence nukleotidů genetika   MeSH
• serin-arginin sestřihové faktory metabolismus   MeSH
• sestřih RNA fyziologie   MeSH
• sestřihové faktory metabolismus   fyziologie   MeSH
• sestřihový faktor U2AF metabolismus   MeSH
• spliceozomy metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• místa sestřihu RNA MeSH
• proteiny vázající RNA MeSH
• serin-arginin sestřihové faktory MeSH
• sestřihové faktory MeSH
• sestřihový faktor U2AF MeSH
• SRSF1 protein, human MeSH Prohlížeč
• U2AF1 protein, human MeSH Prohlížeč

For more than three decades, researchers have known that consensus splice sites alone are not sufficient regulatory elements to provide complex splicing regulation. Other regulators, so-called splicing regulatory elements (SREs) are needed. Most importantly, their sequence variants often underlie the development of various human disorders. However, due to their variable location and high degeneracy, these regulatory sequences are also very difficult to recognize and predict. Many different approaches aiming to identify SREs have been tried, often leading to the development of in silico prediction tools. While these tools were initially expected to be helpful to identify splicing-affecting mutations in genetic diagnostics, we are still quite far from meeting this goal. In fact, most of these tools are not able to accurately discern the SRE-affecting pathological variants from those not affecting splicing. Nonetheless, several recent evaluations have given appealing results (namely for EX-SKIP, ESRseq and Hexplorer predictors). In this review, we aim to summarize the history of the different approaches to SRE prediction, and provide additional validation of these tools based on patients' clinical data. Finally, we evaluate their usefulness for diagnostic settings and discuss the challenges that have yet to be met.

• Klíčová slova
• evaluation of prediction tools, in silico predictions, mutation, pre-mRNA splicing, splicing aberration, splicing regulatory elements, variants of unknown significance,
• MeSH
• diagnostické techniky molekulární metody   trendy   MeSH
• genetické nemoci vrozené * MeSH
• lidé MeSH
• místa sestřihu RNA * MeSH
• mutace * MeSH
• prekurzory RNA genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• místa sestřihu RNA * MeSH
• prekurzory RNA MeSH

Mutations in the first nucleotide of exons (E(+1)) mostly affect pre-mRNA splicing when found in AG-dependent 3' splice sites, whereas AG-independent splice sites are more resistant. The AG-dependency, however, may be difficult to assess just from primary sequence data as it depends on the quality of the polypyrimidine tract. For this reason, in silico prediction tools are commonly used to score 3' splice sites. In this study, we have assessed the ability of sequence features and in silico prediction tools to discriminate between the splicing-affecting and non-affecting E(+1) variants. For this purpose, we newly tested 16 substitutions in vitro and derived other variants from literature. Surprisingly, we found that in the presence of the substituting nucleotide, the quality of the polypyrimidine tract alone was not conclusive about its splicing fate. Rather, it was the identity of the substituting nucleotide that markedly influenced it. Among the computational tools tested, the best performance was achieved using the Maximum Entropy Model and Position-Specific Scoring Matrix. As a result of this study, we have now established preliminary discriminative cut-off values showing sensitivity up to 95% and specificity up to 90%. This is expected to improve our ability to detect splicing-affecting variants in a clinical genetic setting.

• MeSH
• agamaglobulinemie genetika   MeSH
• bodová mutace * MeSH
• exony MeSH
• genetické nemoci vázané na chromozom X genetika   MeSH
• HeLa buňky MeSH
• lidé MeSH
• místa sestřihu RNA * MeSH
• modely genetické MeSH
• molekulární sekvence - údaje MeSH
• počítačová simulace MeSH
• proteinkinasa BTK MeSH
• sekvenční analýza DNA MeSH
• sestřih RNA MeSH
• software * MeSH
• tyrosinkinasy genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• hodnotící studie MeSH
• práce podpořená grantem MeSH
• Názvy látek
• místa sestřihu RNA * MeSH
• proteinkinasa BTK MeSH
• tyrosinkinasy MeSH

Higher order RNA structures can mask splicing signals, loop out exons, or constitute riboswitches all of which contributes to the complexity of splicing regulation. We identified a G to A substitution between branch point (BP) and 3' splice site (3'ss) of Saccharomyces cerevisiae COF1 intron, which dramatically impaired its splicing. RNA structure prediction and in-line probing showed that this mutation disrupted a stem in the BP-3'ss region. Analyses of various COF1 intron modifications revealed that the secondary structure brought about the reduction of BP to 3'ss distance and masked potential 3'ss. We demonstrated the same structural requisite for the splicing of UBC13 intron. Moreover, RNAfold predicted stable structures for almost all distant BP introns in S. cerevisiae and for selected examples in several other Saccharomycotina species. The employment of intramolecular structure to localize 3'ss for the second splicing step suggests the existence of pre-mRNA structure-based mechanism of 3'ss recognition.

• MeSH
• Ascomycota genetika   MeSH
• fungální RNA chemie   MeSH
• introny * MeSH
• kofilin 1 genetika   MeSH
• konformace nukleové kyseliny MeSH
• místa sestřihu RNA * MeSH
• molekulární sekvence - údaje MeSH
• Saccharomyces cerevisiae - proteiny genetika   MeSH
• Saccharomyces cerevisiae genetika   MeSH
• sekvence nukleotidů MeSH
• sestřih RNA * MeSH
• teplota MeSH
• ubikvitin konjugující enzymy genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• COF1 protein, S cerevisiae MeSH Prohlížeč
• fungální RNA MeSH
• kofilin 1 MeSH
• místa sestřihu RNA * MeSH
• Saccharomyces cerevisiae - proteiny MeSH
• UBC13 protein, S cerevisiae MeSH Prohlížeč
• ubikvitin konjugující enzymy MeSH