Sik (BRK) phosphorylates Sam68 in the nucleus and negatively regulates its RNA binding ability
Sik (BRK) phosphorylates Sam68 in the nucleus and negatively regulates its RNA binding ability
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DOI：
10.1128/mcb.20.16.6114-6126.2000
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发表时间：
2000-08-01
影响因子：
5.3
通讯作者：
Tyner, AL
中科院分区：
文献类型：
--
作者：
Derry, JJ;Richard, S;Tyner, AL
Sik（小鼠Src相关肠激酶）及其同源物BRK（人乳腺肿瘤激酶）是细胞内酪氨酸激酶，与Src家族有远亲关系，具有相似的结构，但它们缺乏肉豆肉酰化信号。在这里，我们证明了Sik和BRK与RNA结合蛋白Sam68 （Src在有丝分裂期间相关，68 kDa）相关联，我们发现Sik通过其SH3和SH2结构域与Sam68相互作用，并且Sam68富含脯氨酸的P3区域是Sik和BRK SH3结合所必需的。在转化的HT29腺癌细胞细胞系中，内源性BRK和Sam68共定位于Sam68 SLM核体（snb）中，而转染的Sik和Sam68则弥散定位于未转化的NMuMG乳腺上皮细胞的核质中。转染的丝蛋白磷酸化HT29细胞和NMuMG细胞核质中SNBs中的Sam68。在功能研究中，Sik的表达使Sam68丧失了转录RNA和作为细胞Rev同源物的能力，而Sam68在有丝分裂过程中是Src家族激酶的底物，而Sik/BRK是第一个被发现的酪氨酸激酶，它可以磷酸化Sam68并调节其在细胞核内的活性，在细胞周期的大部分时间里，Sam68都存在于细胞核内。
Sik (mouse Src-related intestinal kinase) and its orthologue BRK (human breast tumor kinase) are intracellular tyrosine kinases that are distantly related to the Src family and have a similar structure, but they lack the myristoylation signal. Here we demonstrate that Sik and BRK associate with the RNA binding protein Sam68 (Src associated during mitosis, 68 kDa), We found that Sik interacts with Sam68 through its SH3 and SH2 domains and that the proline-rich P3 region of Sam68 is required for Sik and BRK SH3 binding. In the transformed HT29 adenocarcinoma cell cell Line, endogenous BRK and Sam68 colocalize in Sam68 SLM nuclear bodies (SNBs), while transfected Sik and Sam68 are localized diffusely in the nucleoplasm of nontransformed NMuMG mammary epithelial tells. Transfected Sik phosphorylates Sam68 in SNBs in HT29 cells and in the nucleoplasm of NMuMG cells. in functional studies, expression of Sik abolished the ability of Sam68 to hind RNA and act as a cellular Rev homologue, While Sam68 is a substrate for Src family kinases during mitosis, Sik/BRK is the first identified tyrosine kinase that can phosphorylate Sam68 and regulate its activity within the nucleus, where it resides during most of the cell cycle.