Neurochem Res. 2013 Nov;38(11):2427-32. doi: 10.1007/s11064-013-1155-4.
The Calcyclin binding protein and Siah-1 interacting protein (CacyBP/SIP) protein is highly expressed in mammalian brain as well as in neuroblastoma NB2a cells and pheochromocytoma PC12 cells. This protein interacts with several targets such as cytoskeletal proteins or ERK1/2 kinase and seems to be involved in many cellular processes. In this work we examined a post-translational modification of CacyBP/SIP which might have an effect on its function. Since theoretical analysis of the amino acid sequence of CacyBP/SIP indicated several lysine residues which could potentially be sumoylated we checked experimentally whether this protein might be modified by SUMO attachment. We have shown that indeed CacyBP/SIP bound the E2 SUMO ligase, Ubc9, in neuroblastoma NB2a cell extract and was sumoylated in these cells. By fractionation of NB2a cell extract we have found that, contrary to the majority of SUMO-modified proteins, sumoylated CacyBP/SIP is present in the cytoplasmic and not in the nuclear fraction. We have also established that lysine 16 is the residue which undergoes sumoylation in the CacyBP/SIP protein.
钙调素结合蛋白和 Siah-1 相互作用蛋白（CacyBP/SIP）蛋白在哺乳动物大脑以及神经母细胞瘤 NB2a 细胞和嗜铬细胞瘤 PC12 细胞中高度表达。该蛋白与几种靶标相互作用，如细胞骨架蛋白或 ERK1/2 激酶，似乎参与许多细胞过程。在这项工作中，我们研究了 CacyBP/SIP 的一种翻译后修饰，它可能对其功能有影响。由于 CacyBP/SIP 氨基酸序列的理论分析表明有几个赖氨酸残基可能被 SUMO 化，我们实验检查了这种蛋白质是否可能被 SUMO 修饰。我们已经表明，CacyBP/SIP 确实与神经母细胞瘤 NB2a 细胞提取物中的 E2 SUMO 连接酶 Ubc9 结合，并在这些细胞中被 SUMO 化。通过 NB2a 细胞提取物的分级分离，我们发现，与大多数 SUMO 修饰蛋白相反，CacyBP/SIP 的 SUMO 化形式存在于细胞质而不是核部分。我们还确定赖氨酸 16 是 CacyBP/SIP 蛋白中发生 SUMO 化的残基。
