Lutz Y, Jacob M, Fuchs J P
Laboratoire de Génétique Moléculaire des Eucaryotes du CNRS, Strasbourg, France.
Exp Cell Res. 1988 Mar;175(1):109-24. doi: 10.1016/0014-4827(88)90259-5.
A monoclonal antibody obtained after mice were immunized with hnRNP purified from HeLa cells recognizes two polypeptides of Mr 35,000 and 37,000. By immunocytofluorescence, these antigens can be visualized only in cells previously heat shocked at 45 degrees C for 5 or 10 min, although they are present at the same level in unstressed and stressed cells. The signal, which is mostly concentrated in the interchromatin space, where hnRNP fibrils are located, does not accumulate with time and disappears 4 to 5 h after heat shock. Discrimination between the two types of hnRNP substructures, the 30-50 S monoparticles and the nuclear matrix fibrils, based on differential sensitivity to salt or ribonuclease treatment, showed that in unstressed cells the antigens behave as monoparticle proteins. In contrast, in heat-shocked cells, most 35-37K antigens behave as nuclear matrix proteins. Thus, heat shock seems to induce a rapid and reversible switch of these two antigens from hnRNP monoparticles to the nuclear matrix. The data demonstrate that heat shock, which was previously shown not to alter the overall RNA: protein packaging ratio of hnRNP, induces subtle modifications of their substructure. Such modifications might be of importance since heat shock is known for instance to affect pre-mRNA processing.
用从HeLa细胞中纯化的hnRNP免疫小鼠后获得的单克隆抗体识别出分子量为35,000和37,000的两种多肽。通过免疫细胞荧光法，这些抗原仅在先前于45℃热休克5或10分钟的细胞中可见，尽管它们在未受应激和受应激的细胞中以相同水平存在。信号主要集中在hnRNP纤维所在的染色质间空间，不会随时间积累，并在热休克后4至5小时消失。基于对盐或核糖核酸酶处理的不同敏感性对两种类型的hnRNP亚结构（30 - 50 S单颗粒和核基质纤维）进行区分，结果表明在未受应激的细胞中，抗原表现为单颗粒蛋白。相反，在热休克细胞中，大多数35 - 37K抗原表现为核基质蛋白。因此，热休克似乎诱导了这两种抗原从hnRNP单颗粒到核基质的快速且可逆的转变。数据表明，先前显示不会改变hnRNP总体RNA:蛋白质包装比例的热休克诱导了其亚结构的细微修饰。由于热休克已知会影响例如前体mRNA加工，所以这种修饰可能很重要。
