Nikolakaki E, Meier J, Simos G, Georgatos S D, Giannakouros T
Laboratory of Biochemistry, School of Chemistry, The Aristotelian University of Thessaloniki, Thessaloniki 54 006, Greece.
J Biol Chem. 1997 Mar 7;272(10):6208-13. doi: 10.1074/jbc.272.10.6208.
The lamin B receptor (LBR) is an integral protein of the inner nuclear membrane that is modified at interphase by a nuclear envelope-bound protein kinase. This enzyme (RS kinase) specifically phosphorylates arginine-serine dipeptide motifs located at the NH2-terminal domain of LBR and regulates its interactions with other nuclear envelope proteins. To compare the phosphorylation state of LBR during interphase and mitosis, we performed phosphopeptide mapping of in vitro and in vivo 32P-labeled LBR and analyzed a series of recombinant proteins and synthetic peptides. Our results show that LBR undergoes two types of mitotic phosphorylation mediated by the RS and the p34(cdc2) protein kinases, respectively. The RS kinase modifies similar sites at interphase and mitosis (i.e. Ser76, Ser78, Ser80, Ser82, Ser84), whereas p34(cdc2) mainly phosphorylates Ser71. These findings clarify the phosphorylation state of LBR during the cell cycle and provide new information for understanding the mechanisms responsible for nuclear envelope assembly and disassembly.
核纤层蛋白B受体（LBR）是内核膜的一种整合蛋白，在间期被一种与核膜结合的蛋白激酶修饰。这种酶（RS激酶）特异性地磷酸化位于LBR氨基末端结构域的精氨酸 - 丝氨酸二肽基序，并调节其与其他核膜蛋白的相互作用。为了比较LBR在间期和有丝分裂期间的磷酸化状态，我们对体外和体内32P标记的LBR进行了磷酸肽图谱分析，并分析了一系列重组蛋白和合成肽。我们的结果表明，LBR分别经历了由RS激酶和p34（cdc2）蛋白激酶介导的两种有丝分裂磷酸化类型。RS激酶在间期和有丝分裂时修饰相似的位点（即Ser76、Ser78、Ser80、Ser82、Ser84），而p34（cdc2）主要磷酸化Ser71。这些发现阐明了细胞周期中LBR的磷酸化状态，并为理解负责核膜组装和拆卸的机制提供了新信息。
