HNRNP-I, THE POLYPYRIMIDINE TRACT-BINDING PROTEIN - DISTINCT NUCLEAR-LOCALIZATION AND ASSOCIATION WITH HNRNAS
HNRNP-I, THE POLYPYRIMIDINE TRACT-BINDING PROTEIN - DISTINCT NUCLEAR-LOCALIZATION AND ASSOCIATION WITH HNRNAS
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DOI：
10.1093/nar/20.14.3671
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发表时间：
1992-07-25
影响因子：
14.9
通讯作者：
DREYFUSS, G
中科院分区：
文献类型：
--
作者：
GHETTI, A;PINOLROMA, S;DREYFUSS, G
许多hnRNP蛋白和snRNP与真核细胞核中的hnRNA相互作用，并影响hnRNA的命运及其加工成mRNA。脊椎动物细胞hnRNP复合物中至少有20种丰富的蛋白质，它们在特定hnRNA上的结构和排列可能对前体mRNA的加工很重要。hnRNP I是一种碱性蛋白。SDS-PAGE测得分子量为58，000道尔顿，是一种丰富的hnRNA结合蛋白。制备hnRNP I的单克隆抗体，分离hnRNP I的全长cDNA克隆并测序。hnRNP I的序列（59，632道尔顿和pI 9.86）表明它与先前描述的多聚嘧啶片段结合蛋白（PTB）相同，并表明它与hnRNP L高度相关。这两个蛋白质的序列，I和L，定义了一个新的家庭的hnRNP蛋白质内的大超家族的RNP共识RNA结合蛋白。在这里，我们描述的实验，揭示了新的和独特的属性的协会hnRNP I/PTB与hnRNP复合物和其细胞定位。微球菌核酸酶消化显示，hnRNP I，沿着hnRNP S和P，通过核酸酶消化比大多数其他hnRNP蛋白更容易从hnRNP复合物中释放。这种核酸酶超敏性表明hnRNP I结合到在复合物中特别暴露的hnRNA区域。免疫荧光显微镜显示，hnRNP我被发现在核质中，但另外高浓度检测到一个离散的核仁周围结构。因此，PTB是结合前mRNA的主要蛋白质之一;它结合到hnRNA-蛋白质复合物的核酸酶超敏感区域，并显示出核定位的新模式。
Many hnRNP proteins and snRNPs interact with hnRNA in the nucleus of eukaryotic cells and affect the fate of hnRNA and its processing into mRNA. There are at least 20 abundant proteins in vertebrate cell hnRNP complexes and their structure and arrangement on specific hnRNAs is likely to be important for the processing of pre-mRNAs. hnRNP I, a basic protein of ca. 58,000 daltons by SDS-PAGE, is one of the abundant hnRNA-binding proteins. Monoclonal antibodies to hnRNP I were produced and full length cDNA clones for hnRNP I were isolated and sequenced. The sequence of hnRNP I (59,632 daltons and pI 9.86) demonstrates that it is identical to the previously described polypyrimidine tract-binding protein (PTB) and shows that it is highly related to hnRNP L. The sequences of these two proteins, I and L, define a new family of hnRNP proteins within the large superfamily of the RNP consensus RNA-binding proteins. Here we describe experiments which reveal new and unique properties on the association of hnRNP I/PTB with hnRNP complexes and on its cellular localization. Micrococcal nuclease digestions show that hnRNP I, along with hnRNP S and P, is released from hnRNP complexes by nuclease digestion more readily than most other hnRNP proteins. This nuclease hypersensitivity suggests that hnRNP I is bound to hnRNA regions that are particularly exposed in the complexes. Immunofluorescence microscopy shows that hnRNP I is found in the nucleoplasm but in addition high concentrations are detected in a discrete perinucleolar structure. Thus, the PTB is one of the major proteins that bind pre-mRNAs; it is bound to nuclease-hypersensitive regions of the hnRNA-protein complexes and shows a novel pattern of nuclear localization.