Laboratory for Malignancy Control Research, Medical Innovation Center, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Laboratory of Molecular Medicinal Science, Department of Pharmaceutical Sciences, Ritsumeikan University, Shiga, Japan.
Genes Cells. 2020 May;25(5):327-333. doi: 10.1111/gtc.12756. Epub 2020 Feb 25.
SRSF4 is one of the members of serine-/arginine (SR)-rich protein family involved in both constitutive and alternative splicing. SRSF4 is localized in the nucleus with speckled pattern, but its nuclear localization signal was not determined. Here, we have identified nuclear localization signals (NLSs) of SRSF4 by using a pyruvate kinase fusion system. As expected, arginine-/serine (RS)-rich domain of SRSF4 confers nuclear localization activity when it is fused to PK protein. We then further delineated the minimum sequences for nuclear localization in RS domain of SRSF4. Surprisingly, RS-rich region does not always have a nuclear localization activity. In addition, basic amino acid stretches that resemble to classical-type NLSs were identified. These results strongly suggest that SRSF4 protein uses two different nuclear import pathways with multiple NLSs in RS domain.
SRSF4 是参与组成型和选择性剪接的丝氨酸/精氨酸（SR）富含蛋白家族的成员之一。SRSF4 定位于具有斑点模式的核内，但尚未确定其核定位信号。在这里，我们使用丙酮酸激酶融合系统鉴定了 SRSF4 的核定位信号（NLS）。正如预期的那样，当 SRSF4 的富含精氨酸/丝氨酸（RS）结构域与 PK 蛋白融合时，它赋予核定位活性。然后，我们进一步描绘了 SRSF4 RS 结构域中核定位的最小序列。令人惊讶的是，富含 RS 的区域并不总是具有核定位活性。此外，还鉴定了类似于经典 NLS 的碱性氨基酸延伸。这些结果强烈表明，SRSF4 蛋白使用 RS 结构域中的两个不同的核输入途径和多个 NLS。
