Verheijen R, Kuijpers H, Vooijs P, Van Venrooij W, Ramaekers F
Department of Pathology, Radboud Hospital, Nijmegen, The Netherlands.
J Cell Sci. 1986 Dec;86:173-90. doi: 10.1242/jcs.86.1.173.
Earlier studies suggested that the 70K (70 X 10(3) Mr) polypeptide is a nuclear matrix (associated) protein since it is the only U1 RNP-associated antigen that is not released from the nucleus after treatment of the cell with, successively, detergents, DNase I and/or RNase A and high salt. The possibility that the 70K protein functions in the binding of U1 RNP to the nuclear matrix is now further substantiated by the finding that U1 RNP particles that did or did not contain the 70K protein could be isolated, depending on the method of isolation. When U1 RNP particles were obtained by means of sonic disruption of the nucleus they contained the 70K polypeptide, whereas particles that were isolated by extraction at room temperature and a slightly alkaline pH lacked the 70K protein but contained the intact U1 RNA and the other U1 RNA-associated proteins. During interphase the localization of the 70K protein is restricted to the nucleus, giving a dot-like distribution pattern with exclusion of the nucleoli. During prophase to late anaphase the protein is dispersed throughout the entire cytoplasm with the exception of the chromatin regions. Immunofluorescence studies, using a monoclonal anti-70K antibody in combination with human autoimmune sera that react with U1 RNA-associated proteins, demonstrate that the 70K protein is localized in those areas of the cell where other U RNP proteins occur, also during mitosis. Topoisomerase I and nuclear lamins, typical nuclear matrix proteins, show completely different distribution patterns in all phases of the cell cycle. Assembly of the nuclear envelope is attended by the re-formation of the clustered appearance of the 70K antigen. These results suggest that, although associated with the nuclear matrix fraction in interphase cells, the 70K protein remains associated with the U1 RNP particles during cell division.
早期研究表明，70K（70×10³Mr）多肽是一种核基质（相关）蛋白，因为它是唯一一种在用去污剂、DNA酶I和/或RNA酶A以及高盐依次处理细胞后仍未从细胞核中释放出来的U1 RNP相关抗原。现在，根据分离方法可以分离出含有或不含有70K蛋白的U1 RNP颗粒这一发现，进一步证实了70K蛋白在U1 RNP与核基质结合中发挥作用的可能性。当通过超声破碎细胞核获得U1 RNP颗粒时，它们含有70K多肽，而在室温及略碱性pH条件下通过提取分离得到的颗粒则缺乏70K蛋白，但含有完整的U1 RNA和其他U1 RNA相关蛋白。在间期，70K蛋白的定位仅限于细胞核，呈现点状分布模式，核仁除外。在前期到后期，该蛋白分散在整个细胞质中，染色质区域除外。免疫荧光研究使用单克隆抗70K抗体结合与U1 RNA相关蛋白反应的人类自身免疫血清，表明70K蛋白也存在于有丝分裂期间细胞中其他U RNP蛋白所在的区域。拓扑异构酶I和核纤层蛋白是典型的核基质蛋白，在细胞周期的所有阶段都表现出完全不同的分布模式。核膜组装伴随着70K抗原簇状外观的重新形成。这些结果表明，尽管70K蛋白在间期细胞中与核基质部分相关，但在细胞分裂期间它仍与U1 RNP颗粒相关。
