Abstract
Serine/arginine protein kinases (SRPKs) phosphorylate Arg/Ser dipeptide-containing proteins that play crucial roles in a broad spectrum of basic cellular processes. The existence of a large internal spacer sequence that separates the bipartite kinase catalytic core and anchors the kinases in the cytoplasm is a unique structural feature of SRPKs. Here, we report that exposure of HeLa and T24 cells to DNA damage inducers triggers the nuclear translocation of SRPK1 and SRPK2. Furthermore, we show that nuclear SRPKs did not protect from, but on the contrary, mediated the cytotoxic effects of genotoxic agents, such as 5-fluorouracil (5-FU) and cisplatin. Confirming previous data showing that the kinase activity is essential for the entry of SRPKs into the nucleus, SRPIN340, a selective SRPK1/2 inhibitor, blocked the nuclear accumulation of the kinases, thus diminishing the cytotoxic effects of the drugs. ATR/ATM-dependent phosphorylation of threonine 326 and serine 408 in the spacer domain of SRPK1 was essential for the redistribution of the kinase to the nucleus. Substitution of either of these two residues to alanine or inhibition of ATR/ATM kinase activity abolished nuclear localization of SRPK1 and conferred tolerance to 5-FU treatment. These findings suggest that SRPKs may play an important role in linking cellular signaling to DNA damage in eukaryotic cells.
Highlights
Serine/arginine protein kinases (SRPKs) constitute a subfamily of serine-threonine kinases that phosphorylate serine residues residing in arginine-serine dipeptide motifs, known as RS domains [1,2]
Both SRPK1 and SRPK2 are primarily localized in the cytoplasm, while deletion of the spacer sequence forces the nuclear accumulation of SRPKs, with harmful effects ranging from the aggregation of the splicing factors and defects in the splicing machinery in mammalian cells [7,8,9] to inhibition of cell growth in yeast [10]
To further characterize the effectiveness and possibly find a common denominator of the various stress signals, we designed a series of immunofluorescence experiments to test the outcome of stress agents on the SRPK1 redistribution from the cytoplasm to the nucleus, focusing mainly on two widely used chemotherapeutic drugs, namely, 5-FU and cisplatin
Summary
Serine/arginine protein kinases (SRPKs) constitute a subfamily of serine-threonine kinases that phosphorylate serine residues residing in arginine-serine dipeptide motifs, known as RS domains [1,2]. Considered to exclusively regulate pre-mRNA splicing through the phosphorylation of SR splicing factors, SRPKs are known to be involved in various cellular processes [1,3]. As the mammalian genome contains more than a hundred RS domain-containing proteins [4], this pleiotropic mode of action might be related to the phosphorylation of diverse substrates, thereby resulting in the activation of distinct downstream signaling pathways. Several modes of regulation of SRPK function have been described, implying an elaborate cellular control of their activity. All family members share highly conserved kinase domains, which are separated by a unique spacer sequence. Both SRPK1 and SRPK2 are primarily localized in the cytoplasm, while deletion of the spacer sequence forces the nuclear accumulation of SRPKs, with harmful effects ranging from the aggregation of the splicing factors and defects in the splicing machinery in mammalian cells [7,8,9] to inhibition of cell growth in yeast [10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
