Umeda M, Nishitani H, Nishimoto T
Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka 812-8582, Japan.
Gene. 2003 Jan 16;303:47-54. doi: 10.1016/s0378-1119(02)01153-8.
A truncated human RanBPM has been isolated as a protein binding to Ran, Ras-like nuclear small GTPase. Full-sized human RanBPM cDNA which was recently isolated, was found to encode a protein of 90 kDa which comprises a large protein complex. Consistent with this finding, several proteins were found to be co-precipitated with RanBPM by immunoprecipitation analysis. Accordingly, in the present study, we screened the human cDNA library by the two-hybrid method using RanBPM cDNA as bait. One novel protein designated as Twa1 (Two hybrid associated protein No. 1 with RanBPM), and two known proteins, a human homologue (hMuskelin) of mouse Muskelin and HSMpp8 were isolated repeatedly. Twa1 was well conserved through evolution and was localized within the nucleus. Interestingly, in addition to Muskelin and RanBPM, Twa1 was found to possess the LisH-CTLH motif which is detected in proteins involved in microtubule dynamics, cell migration, nucleokinesis and chromosome segregation. These functions overlap with functions suggested for the RanGTPase cycle. Immunoprecipitation and gel-filtration analyses indicated that both Twa1 and hMuskelin did indeed comprise a protein complex with RanBPM. Taken together with the fact that RanBPM interacts with Ran, our present findings suggested that there is an as yet uncovered function of the RanGTPase cycle.
一种截短的人RanBPM已被分离出来，作为一种与Ran（Ras样核小GTP酶）结合的蛋白质。最近分离出的全长人RanBPM cDNA被发现编码一种90 kDa的蛋白质，该蛋白质包含一个大型蛋白质复合物。与这一发现一致，通过免疫沉淀分析发现有几种蛋白质与RanBPM共沉淀。因此，在本研究中，我们以RanBPM cDNA为诱饵，通过双杂交方法筛选人cDNA文库。反复分离出一种名为Twa1（与RanBPM相关的双杂交蛋白1号）的新蛋白质，以及两种已知蛋白质，即小鼠Muskelin的人同源物（hMuskelin）和HSMpp8。Twa1在进化过程中高度保守，定位于细胞核内。有趣的是，除了Muskelin和RanBPM外，还发现Twa1具有LisH-CTLH基序，该基序在参与微管动力学、细胞迁移、核运动和染色体分离的蛋白质中被检测到。这些功能与RanGTP酶循环所暗示的功能重叠。免疫沉淀和凝胶过滤分析表明，Twa1和hMuskelin确实都与RanBPM组成了一个蛋白质复合物。结合RanBPM与Ran相互作用这一事实，我们目前的研究结果表明RanGTP酶循环存在尚未被发现的功能。
