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Zinc‐induced modulation of SRSF 6 activity alters Bim splicing to promote generation of the most potent apoptotic isoform BimS
Author(s) -
Hara Hirokazu,
Takeda Tatsuya,
Yamamoto Nozomi,
Furuya Keisuke,
Hirose Kazuya,
Kamiya Tetsuro,
Adachi Tetsuo
Publication year - 2013
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.12318
Subject(s) - alternative splicing , sr protein , rna splicing , exon , microbiology and biotechnology , gene isoform , biology , endoplasmic reticulum , gene , chemistry , biochemistry , rna
Bim is a member of the pro‐apoptotic BH3‐only Bcl‐2 family of proteins. Bim gene undergoes alternative splicing to produce three predominant splicing variants (BimEL, BimL and BimS). The smallest variant BimS is the most potent inducer of apoptosis. Zinc (Zn 2+ ) has been reported to stimulate apoptosis in various cell types. In this study, we examined whether Zn 2+ affects the expression of Bim in human neuroblastoma SH‐SY5Y cells. Zn 2+ triggered alterations in Bim splicing and induced preferential generation of BimS, but not BimEL and BimL, in a dose‐ and time‐dependent manner. Other metals (cadmium, cobalt and copper) and stresses (oxidative, endoplasmic reticulum and genotoxic stresses) had little or no effect on the expression of BimS. To address the mechanism of Zn 2+ ‐induced preferential generation of BimS, which lacks exon 4, we developed a Bim mini‐gene construct. Deletion analysis using the Bim mini‐gene revealed that predicted binding sites of the SR protein SRSF 6, also known as SR p55, are located in the intronic region adjacent to exon 4. We also found that mutations in the predicted SRSF 6‐binding sites abolished generation of BimS m RNA from the mutated Bim mini‐gene. In addition, a UV cross‐linking assay followed by Western blotting showed that SRSF6 directly bound to the predicted binding site and Zn 2+ suppressed this binding. Moreover, Zn 2+ stimulated SRSF6 hyper‐phosphorylation. TG003, a cdc2‐like kinase inhibitor, partially prevented Zn 2+ ‐induced generation of BimS and SRSF6 hyper‐phosphorylation. Taken together, our findings suggest that Zn 2+ inhibits the activity of SRSF6 and promotes elimination of exon 4, leading to preferential generation of BimS.