Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia.
Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, 119991 Moscow, Russia; Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia.
Biochim Biophys Acta Mol Cell Res. 2020 Feb;1867(2):118601. doi: 10.1016/j.bbamcr.2019.118601. Epub 2019 Nov 13.
The nuclear accumulation of proteins may depend on the presence of short targeting sequences, which are known as nuclear localization signals (NLSs). Here, we found that NLSs are predicted in some cytosolic proteins and examined the hypothesis that these NLSs may be functional under certain conditions. As a model, human cardiac troponin I (hcTnI) was used. After expression in cultured non-muscle or undifferentiated muscle cells, hcTnI accumulated inside nuclei. Several NLSs were predicted and confirmed by site-directed mutagenesis in hcTnI. Nuclear import occurred via the classical karyopherin-α/β nuclear import pathway. However, hcTnI expressed in cultured myoblasts redistributed from the nucleus to the cytoplasm, where it was integrated into forming myofibrils after the induction of muscle differentiation. It appears that the dynamic retention of proteins inside cytoplasmic structures can lead to switching between nuclear and cytoplasmic localization.
蛋白质的核积累可能依赖于短的靶向序列，这些序列被称为核定位信号（NLS）。在这里，我们发现一些胞质蛋白中存在 NLS，并检验了这些 NLS 在某些条件下可能具有功能的假设。以人心肌肌钙蛋白 I（hcTnI）作为模型。在培养的非肌肉或未分化的肌肉细胞中表达后，hcTnI 在内核中积累。通过在 hcTnI 中的定点突变预测和确认了几个 NLS。核输入通过经典的核孔蛋白-α/β核输入途径发生。然而，在培养的成肌细胞中表达的 hcTnI 从核重新分布到细胞质，在肌肉分化诱导后，它整合到正在形成的肌原纤维中。似乎细胞质结构内部蛋白质的动态保留可以导致核定位和细胞质定位之间的转换。
