BCL-2 interacting cell death suppressor (BIS), also known as BAG3, is a multifunctional protein. Aberrant expression and mutation of BIS have been implicated in cancers and myopathy. However, there have only been a few studies on the splicing of BIS pre-mRNA. In the present study, through RT-PCR and sequencing in various cell lines and mouse tissues, we identified for the first time the presence of BIS mRNA isomers in which exon 3 or exons 2–3 are skipped. We also demonstrated that the depletion of SRSF3 promoted the skipping of exon 3 of BIS pre-mRNA in endogenous BIS and the GFP-BIS minigene. SRSF3 specifically interacts with the putative binding sites in exon 3, in which deletion promoted the skipping of exon 3 in the GFP-BIS minigene, which was comparable to the effect of SRSF knockdown. Even though acceleration of exon 3 skipping was not observed in response to various stimuli, SRSF3 depletion, accompanied by the production of a truncated BIS protein, inhibited the nuclear translocation of HSF1, which was restored by the wild-type BIS, not by exon 3-depleted BIS. Therefore, our results suggested that the maintenance of SRSF3 levels and subsequent preservation of the intact BIS protein is an important factor in modulating HSF1 localization upon cellular stress.

中文翻译：

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SRSF3是包含BIS Pre-mRNA外显子3的关键要求

BCL-2相互作用细胞死亡抑制剂（BIS），也称为BAG3，是一种多功能蛋白。BIS的异常表达和突变与癌症和肌病有关。但是，关于BIS pre-mRNA的剪接只有很少的研究。在本研究中，通过RT-PCR和在各种细胞系和小鼠组织中的测序，我们首次确定了BIS mRNA异构体的存在，其中跳过了外显子3或外显子2-3。我们还证明，SRSF3的消耗促进了内源性BIS和GFP-BIS小基因中BIS pre-mRNA外显子3的跳跃。SRSF3与外显子3中的假定结合位点特异性相互作用，其中缺失促进了GFP-BIS小基因中外显子3的跳跃，这与SRSF敲低的效果相当。即使未观察到对各种刺激的外显子3跳跃加速，SRSF3的耗竭，伴随着截短的BIS蛋白的产生，仍抑制了HSF1的核转运，HSF1的核转位是由野生型BIS而非外显子3恢复的。耗尽的BIS。因此，我们的结果表明，SRSF3水平的维持和完整BIS蛋白的后续保存是在细胞应激时调节HSF1定位的重要因素。