Distinct mechanisms govern the phosphorylation of different SR protein splicing factors

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal

10 Scopus Citations
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Author(s)

  • Yunxin Long
  • Weng Hong Sou
  • Kristen Wing Yu Yung
  • Haizhen Liu
  • Stephanie Winn Chee Wan
  • Qingyun Li
  • Chuyue Zeng
  • Carmen Oi Kwan Law
  • Gordon Ho Ching Chan
  • Jacky Chi Ki Ngo

Related Research Unit(s)

Detail(s)

Original languageEnglish
Pages (from-to)1312-1327
Journal / PublicationJournal of Biological Chemistry
Volume294
Issue number4
Online published26 Nov 2018
Publication statusPublished - 25 Jan 2019

Abstract

Serine-arginine (SR) proteins are essential splicing factors containing a canonical RNA recognition motif (RRM), sometimes followed by a pseudo-RRM, and a C-terminal arginine/ serine-rich (RS) domain that undergoes multisite phosphorylation. Phosphorylation regulates the localization and activity of SR proteins, and thus may provide insight into their differential biological roles. The phosphorylation mechanism of the prototypic SRSF1 by serine-arginine protein kinase 1 (SRPK1) has been well-studied, but little is known about the phosphorylation of other SR protein members. In the present study, interaction and kinetic assays unveiled how SRSF1 and the single RRM-containing SRSF3 are phosphorylated by SRPK2, another member of the SRPK family. We showed that a conserved SRPK-specific substrate-docking groove in SRPK2 impacts the binding and phosphorylation of both SR proteins, and the localization of SRSF3. We identified a nonconserved residue within the groove that affects the kinase processivity. We demonstrated that, in contrast to SRSF1, for which SRPK-mediated phosphorylation is confined to the N-terminal region of the RS domain, SRSF3 phosphorylation sites are spread throughout its entire RS domain in vitro. Despite this, SRSF3 appears to be hypophosphorylated in cells at steady state. Our results suggest that the absence of a pseudo-RRM renders the single RRM- containing SRSF3 more susceptible to dephosphorylation by phosphatase. These findings suggest that the single RRM- and two RRM-containing SR proteins represent two subclasses of phosphopro-teins in which phosphorylation statuses are maintained by unique mechanisms, and pose new directions to explore the distinct roles of SR proteins in vivo.

Citation Format(s)

Distinct mechanisms govern the phosphorylation of different SR protein splicing factors. / Long, Yunxin; Sou, Weng Hong; Yung, Kristen Wing Yu; Liu, Haizhen; Wan, Stephanie Winn Chee; Li, Qingyun; Zeng, Chuyue; Law, Carmen Oi Kwan; Chan, Gordon Ho Ching; Lau, Terrence Chi Kong; Ngo, Jacky Chi Ki.

In: Journal of Biological Chemistry, Vol. 294, No. 4, 25.01.2019, p. 1312-1327.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal