Protein of the SR family of splicing factors binds extensively to exonic Balbiani ring pre-mRNA and accompanies the RNA from the gene to the nuclear pore
Protein of the SR family of splicing factors binds extensively to exonic Balbiani ring pre-mRNA and accompanies the RNA from the gene to the nuclear pore
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DOI：
10.1101/gad.10.22.2881
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发表时间：
1996-11-15
影响因子：
10.5
通讯作者：
Daneholt, B
中科院分区：
文献类型：
--
作者：
AlzhanovaEricsson, AT;Sun, X;Daneholt, B
我们报告的分子克隆和细胞内定位的异质核核糖核蛋白（hnRNP），Ct-hrp 45，前mRNP颗粒在摇蚊的主要组成部分之一。结果表明hrp 45属于SR家族剪接因子，与果蝇SRp 55/B52和人SF 2/ASF具有高度的序列相似性。hrp 45在C.通过免疫细胞学研究tennans唾液腺细胞。hrp 45蛋白在细胞核中含量丰富，而在细胞质中检测不到。hrp 45在特定的前mRNP颗粒，Balbiani环（BR）颗粒的命运，是通过免疫电子显微镜。观察到hrp 45与生长的BR pre-mRNP颗粒相关，并且随着转录物的生长而连续加入，表明hrp 45广泛结合外显子4，其占初级转录物的80-90%。此外，hrp 45保持与核质中的BR RNP颗粒结合，直到颗粒移位通过核孔才释放。因此，hrp 45表现为连接到外显子RNA（可能也连接到内含子）的hnRNP蛋白，而不是连接到剪接体组装和拆卸的剪接体组分。看来，hrp 45，也可能是其他SR家族蛋白质，在前mRNP颗粒的结构组织中起着重要作用，也许不仅参与剪接，而且还参与其他核内事件。
We report on the molecular cloning and intracellular localization of a heterogeneous nuclear ribonucleoprotein (hnRNP), Ct-hrp45, one of the major components of pre-mRNP particles in Chironomus tentans. It is shown that hrp45 belongs to the SR family of splicing factors and exhibits high sequence similarity to Drosophila SRp55/B52 and human SF2/ASF. The distribution of hrp45 within the C. tentans salivary gland cells is studied by immunocytology. The hrp45 protein is found to be abundant in the nucleus, whereas it is undetectable in the cytoplasm. The fate of hrp45 in specific pre-mRNP particles, the Balbiani ring (BR) granules, is revealed by immunoelectron microscopy. It is observed that hrp45 is associated with the growing BR pre-mRNP particles and is being added continuously concomitant with the growth of the transcript, indicating that hrp45 is bound extensively to exon 4, which comprises 80-90% of the primary transcript. furthermore, hrp45 remains bound to the BR RNP particles in the nucleoplasm and is not released until the particles translocate through the nuclear pore. Thus, hrp45 behaves as an hnRNP protein linked to exon RNA (and perhaps also to the introns) rather than as a spliceosome component connected to the assembly and disassembly of spliceosomes. It seems that hrp45, and possibly also other SR family proteins, is playing an important role in the structural organization of pre-mRNP particles and is perhaps participating not only in splicing but also in other intranuclear events.