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Author Notes:

Nicholas T. Seyfried, nseyfri@emory.edu

S. R. K. and D. M. D. conceptualization; S. R. K., C. H., S. S., S. K., H. G., and D. M. D. data curation; S. R. K. formal analysis; N. T. S. funding acquisition; S. R. K. investigation; S. R. K., L. Y., L. P., and D. M. D. methodology; N. T. S. resources; E. D. software; N. T. S. supervision; E. D. visualization; S. R. K. writing–original draft; S. R. K., E. D., L. Y., C. H., S. S., L. P., S. K., H. G., D. M. D., and N. T. S. writing–review and editing.

We thank Anita Corbett and Zachary T. McEachin for their helpful comments in discussion of this work. We also thank Izabela Šuster and Yue Feng for sharing the QKI antibody reagent. Support for this research was provided by funding from the National Institute on Aging (R01AG053960, R01AG061800, and RF1AG062181), the Accelerating Medicines Partnership for AD (U01AG046161 and U01AG061357).

The authors declare that they have no conflicts of interest with the contents of this article.


Research Funding:

S. K. was supported by the Training Program in Biochemistry, Cell and Developmental Biology (T32GM008367) and Emory Neurology Department Training Fellowship (5T32NS007480-19).


  • Science & Technology
  • Life Sciences & Biomedicine
  • Biochemistry & Molecular Biology
  • TDP-43
  • TAU

Phosphorylation regulates arginine-rich RNA-binding protein solubility and oligomerization


Journal Title:



Volume 297, Number 5


, Pages 101306-101306

Type of Work:

Article | Final Publisher PDF


Posttranslational modifications (PTMs) such as phosphorylation of RNA-binding proteins (RBPs) regulate several critical steps in RNA metabolism, including spliceosome assembly, alternative splicing, and mRNA export. Notably, serine-/arginine- (SR)-rich RBPs are densely phosphorylated compared with the remainder of the proteome. Previously, we showed that dephosphorylation of the splicing factor SRSF2 regulated increased interactions with similar arginine-rich RBPs U1-70K and LUC7L3. However, the large-scale functional and structural impact of these modifications on RBPs remains unclear. In this work, we dephosphorylated nuclear extracts using phosphatase in vitro and analyzed equal amounts of detergent-soluble and -insoluble fractions by mass-spectrometry-based proteomics. Correlation network analysis resolved 27 distinct modules of differentially soluble nucleoplasm proteins. We found classes of arginine-rich RBPs that decrease in solubility following dephosphorylation and enrich the insoluble pelleted fraction, including the SR protein family and the SR-like LUC7L RBP family. Importantly, increased insolubility was not observed across broad classes of RBPs. We determined that phosphorylation regulated SRSF2 structure, as dephosphorylated SRSF2 formed high-molecular-weight oligomeric species in vitro. Reciprocally, phosphorylation of SRSF2 by serine/ arginine protein kinase 2 (SRPK2) in vitro decreased high-molecular-weight SRSF2 species formation. Furthermore, upon pharmacological inhibition of SRPKs in mammalian cells, we observed SRSF2 cytoplasmic mislocalization and increased formation of cytoplasmic granules as well as cytoplasmic tubular structures that associated with microtubules by immunocytochemical staining. Collectively, these findings demonstrate that phosphorylation may be a critical modification that prevents arginine-rich RBP insolubility and oligomerization.

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© 2021 The Authors

This is an Open Access work distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/).
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