Phosphorylation of serine/arginine‐rich splicing factor 1 at tyrosine 19 promotes cell proliferation in pediatric acute lymphoblastic leukemia

Abstract

Serine/arginine‐rich splicing factor 1 (SRSF1) has been linked to various human cancers including pediatric acute lymphoblastic leukemia (ALL). Our previous study has shown that SRSF1 potentially contributes to leukemogenesis; however, its underlying mechanism remains unclear. In this study, leukemic cells were isolated from pediatric ALL bone marrow samples, followed by immunoprecipitation assays and mass spectrometry analysis specific to SRSF1. Subcellular localization of the SRSF1 protein and its mutants were analyzed by immunofluorescence staining. Cell growth, colony formation, cell apoptosis, and the cell cycle were investigated using stable leukemic cell lines generated with lentivirus‐mediated overexpressed WT or mutant plasmids. Cytotoxicity of the Tie2 kinase inhibitor was also evaluated. Our results showed the phosphorylation of SRSF1 at tyrosine 19 (Tyr‐19) was identified in newly diagnosed ALL samples, but not in complete remission or normal control samples. Compared to the SRSF1 WT cells, the missense mutants of the Tyr‐19 phosphorylation affected the subcellular localization of SRSF1. In addition, the Tyr‐19 phosphorylation of SRSF1 also led to increased cell proliferation and enhanced colony‐forming properties by promoting the cell cycle. Remarkably, we further identified the kinase Tie2 as a potential therapeutic target in leukemia cells. In conclusion, we identify for the first time that the phosphorylation state of SRSF1 is linked to different phases in pediatric ALL. The Tyr‐19 phosphorylation of SRSF1 disrupts its subcellular localization and promotes proliferation in leukemia cells by driving cell‐cycle progression. Inhibitors targeting Tie2 kinase that could catalyze Tyr‐19 phosphorylation of SRSF1 offer a promising therapeutic target for treatment of pediatric ALL.

Structure of SRSF1 RRM1 bound to RNA reveals an unexpected bimodal mode of interaction and explains its involvement in SMN1 exon7 splicing

“…Our results strongly suggest that this effect could originate from the involvement of the domain extremity in binding CA motifs. Moreover, our data can also explain the effect of the phosphorylation of Tyr19 in promoting cell proliferation in pediatric acute lymphoblastic leukemia 41 . Based on the structure of the RRM1 bound to RNA, it is likely that this phosphorylation may prevent the binding of the recognized cytosine by repulsing the negatively charged RNA phosphate of C 3 and therefore the binding of SRSF1 RRM1 to RNA (Fig.…”

Splicing to Keep Cycling: The Importance of Pre-mRNA Splicing during the Cell Cycle

“…Phosphorylation of the splicing factor SRSF1 was shown in HeLa cells to regulate its function in pre-mRNA splicing [71] and to lead to a change in its subcellular localization in pediatric acute lymphoblastic leukemia cells [72]. In detail, phosphorylation on Tyr-19 by kinase TIE2 allowed cell cycle entry [72].…”

“…Phosphorylation of the splicing factor SRSF1 was shown in HeLa cells to regulate its function in pre-mRNA splicing [71] and to lead to a change in its subcellular localization in pediatric acute lymphoblastic leukemia cells [72]. In detail, phosphorylation on Tyr-19 by kinase TIE2 allowed cell cycle entry [72]. Furthermore mutating Tyr-19 resulted in cell-cycle arrest in the G0/G1 phase [72], while depleting DT40 cells of SRSF1 led to G2 cell cycle arrest [73].…”

Effect of Graphene and Graphene Oxide on Airway Barrier and Differential Phosphorylation of Proteins in Tight and Adherens Junction Pathways

“…Also, in the context of development of severe asthma, KEGG enrichment of the spliceosome (mRNAs; SF3A1, SNRPE, SF3B4) has been observed [ 40 ]. Specific proteins in the KEGG pathway included ACIN1, serine/arginine-rich splicing factors, and Ubiquitin specific peptidase, the differential expression of which have been associated with altered cell proliferation and poor cancer prognosis, among others [ 41 , 42 , 43 ]. Another specific protein, SRSF6 (serine and arginine rich splicing factor 6), observed in our enrichment analysis, has also been shown to be dysregulated in ASM cells from asthmatic horses [ 44 ].…”