Fackelmayer F O, Richter A
Department of Biology, University of Konstanz, FRG.
Biochemistry. 1994 Aug 30;33(34):10416-22. doi: 10.1021/bi00200a024.
The scaffold attachment factor A (SAF-A; Romig et al., 1992), a human nuclear protein which specifically binds vertebrate SAR (scaffold attached region) DNA, is identical with hnRNP-U (Kiledjian & Dreyfuss, 1992). In this paper, we report on the purification of two forms of this protein that can be chromatographically separated. We show that the purified proteins represent two isoforms, form 1 and form 2 hnRNP-U, which differ in their primary structure. Both isoforms bind to double- and single-stranded DNA and RNA. In addition, they form higher ordered nucleic acid/protein complexes and specifically bind and aggregate the human SAR element MII at physiological ionic strengths. Electron microscopic analysis shows that the isoforms differ from each other, as form 1 hnRNP-U aggregates into long unbranched filamentous protein/DNA complexes whereas form 2 hnRNP-U aggregates as spheres with an average diameter of 35 nm.
支架附着因子A（SAF-A；Romig等人，1992年）是一种特异性结合脊椎动物支架附着区域（SAR）DNA的人类核蛋白，与核不均一核糖核蛋白U（hnRNP-U；Kiledjian和Dreyfuss，1992年）相同。在本文中，我们报道了该蛋白两种可通过色谱法分离的形式的纯化过程。我们表明，纯化后的蛋白代表两种亚型，即1型和2型hnRNP-U，它们的一级结构不同。两种亚型均能结合双链和单链DNA及RNA。此外，它们能形成更高级别的核酸/蛋白质复合物，并在生理离子强度下特异性结合并聚集人类SAR元件MII。电子显微镜分析表明，这两种亚型彼此不同，因为1型hnRNP-U聚集成无分支的长丝状蛋白质/DNA复合物，而2型hnRNP-U聚集成平均直径为35nm的球体。
