Matunis M J, Xing J, Dreyfuss G
Howard Hughes Medical Institute, University of Pennsylvania School of Medicine, Philadelphia 19104-6148.
Nucleic Acids Res. 1994 Mar 25;22(6):1059-67. doi: 10.1093/nar/22.6.1059.
More than 20 different heterogeneous nuclear ribonucleoproteins (hnRNPs) are associated with pre-mRNAs in the nucleus of mammalian cells and these proteins appear to influence pre-mRNA processing and other aspects of mRNA metabolism and transport. The arrangement of hnRNP proteins on pre-mRNAs is likely to be unique for each RNA and may be determined by the different RNA-binding preferences of each of these proteins. hnRNP F (M(r) = 53 kD, pI = 6.1) and hnRNP H (M(r) = 56 kD, pI = 6.7-7.1) are abundant components of immunopurified hnRNP complexes and they have distinct nucleic acid binding properties. Unlike other hnRNP proteins which display a varying range of affinities for different ribonucleotidehomopolymers and ssDNA, hnRNP F and hnRNP H bind only to poly(rG) in vitro. hnRNP F and hnRNP H were purified from HeLa cells by poly(rG) affinity chromatography and oligonucleotides derived from peptide sequences were used to isolate a cDNA encoding hnRNP F. The predicted amino acid sequence of hnRNP F revealed a novel protein with three repeated domains related to the RNP consensus sequence RNA-binding domain. Monoclonal antibodies produced against bacterially expressed hnRNP F were specific for both hnRNP F and hnRNP H and recognized related proteins in divergent organisms, including in the yeast Saccharomyces cerevisiae. hnRNP F and hnRNP H are thus highly related immunologically and they share identical peptides. Interestingly, immunofluorescence microscopy revealed that hnRNP F and hnRNP H are concentrated in discrete regions of the nucleoplasm, in contrast to the general nucleoplasmic distribution of previously characterized hnRNP proteins. The unique RNA-binding properties, amino acid sequence and distinct intranuclear localization of hnRNP F and hnRNP H make them novel hnRNP proteins that are likely to be important for the processing of RNAs containing guanosine-rich sequences.
20多种不同的不均一核糖核蛋白（hnRNP）与哺乳动物细胞核中的前体mRNA相关联，这些蛋白质似乎会影响前体mRNA的加工以及mRNA代谢和运输的其他方面。hnRNP蛋白在前体mRNA上的排列可能对每种RNA都是独特的，并且可能由这些蛋白质各自不同的RNA结合偏好决定。hnRNP F（分子量=53kD，等电点=6.1）和hnRNP H（分子量=56kD，等电点=6.7 - 7.1）是免疫纯化的hnRNP复合物的丰富成分，它们具有独特的核酸结合特性。与其他对不同核糖核苷酸同聚物和单链DNA表现出不同亲和力范围的hnRNP蛋白不同，hnRNP F和hnRNP H在体外仅与聚（rG）结合。通过聚（rG）亲和色谱从HeLa细胞中纯化出hnRNP F和hnRNP H，并使用源自肽序列的寡核苷酸分离出编码hnRNP F的cDNA。hnRNP F的预测氨基酸序列揭示了一种新型蛋白质，具有与RNP共有序列RNA结合结构域相关的三个重复结构域。针对细菌表达的hnRNP F产生的单克隆抗体对hnRNP F和hnRNP H都具有特异性，并识别不同生物体中的相关蛋白质，包括酿酒酵母。因此，hnRNP F和hnRNP H在免疫学上高度相关，并且它们共享相同的肽段。有趣的是，免疫荧光显微镜显示，与先前表征的hnRNP蛋白的一般核质分布相反，hnRNP F和hnRNP H集中在核质的离散区域。hnRNP F和hnRNP H独特的RNA结合特性、氨基酸序列和不同的核内定位使其成为新型的hnRNP蛋白，可能对富含鸟苷序列的RNA的加工很重要。
