Subnucleolar Distribution and Transportation of U3 snoRNA in the Nucleolus of Pisum sativum

豌豆细胞核仁中U3 snoRNA的分布和转运(英文)

Processing of pre-rRNA is one of the major events taking place In the nucleolus. U3 snoRNA, an rRNA spliceosomal factor, is suggested to be essential in the first cleavage step of the 5' ETS sequence in the processing of pre-rRNA. Identification of U3 in the nucleolus provides a piece of indirect evidence for pre-rRNA processing site and transportation of processing products. In the present study, subnucleolar distribution of U3 snoRNA in the nucleolus of Pisum sativum L. was studied by in situ hybridization with a U3 snoRNA probe. The results showed that the U3 labeling signals were distributed throughout dense fibrillar components (DFCs) and granular components (GCs), while no signal was found in fibrillar centers (FCs). When treated with actinomycine D (AMD), the labeling signals were decreased. Along with the increase of the AMD treatment time, the labeling signals became fewer and they were found in the distal regions of DFC and GC. Our results indicated that pre-rRNA splicing took place in the regions of DFC and GC, and the transportation of pre-rRNA processing products was from the regions around FCs towards the distal regions.

rRNA前体剪切是发生在核仁中的重要生物学事件。U3snoRNA作为rRNA的一个剪切因子被认为是rRNA前体剪切第一步 ,即 5′ETS剪切所必需的。鉴定U3能够为确定rRNA前体剪切位点和剪切产物转运提供间接证据。本文利用原位杂交技术研究了豌豆 (PisumsativumL .)核仁中U3snoRNA的分布和转运。结果表明 ,U3snoRNA分布在致密纤维组分 (densefibrillarcomponent,DFC)和颗粒组分 (granularcomponent,GC)中 ,在纤维中心 (fibrillarcen ter,FC)没有分布。当用放线菌素D (actinomycinD ,AMD)处理豌豆根端分生细胞时 ,rDNA转录受到抑制 ,标记信号减弱。随着AMD处理时间的延长 ,标记信号逐渐变弱并出现在DFC远轴区域和GC区域。本文结果提示 ,rRNA前体剪切发生在DFC和GC区域 。