类胀泡结构是合成核糖核酸多聚酶Ⅱ转录产物的核内结构

THE PUFFLIKE STRUCTURE: AN INTRANUCLEAR STRUCTURE FOR SYNTHESIS OF RIBONUCLEIC ACID POLYMERASE Ⅱ TRANSCRIPTS AS REVEALED BY THE 5BROMOURIDINE5′TRIPHOSPHATE LABELLING AND IMMUNOELECTRON MICROSCOPY

采用可定位研究新生ＲＮＡ多聚酶Ⅱ（ＲＰⅡ）转录产物的溴尿嘧啶核苷三磷酸（ＢｒＵＴＰ）标记技术，对洋葱（ＡｌｉｕｍｃｅｐａＬ．）根端分生组织细胞核中的类胀泡结构（ＰＬＳ）进行了研究。经ＢｒＵＴＰ和抗ＢｒｄＵ抗体标记后，在电镜下观察到ＰＬＳ中存在大量的金颗粒，说明该结构中进行着旺盛的ＲＰⅡ转录产物的合成；经α鹅膏蕈碱（αＡ，１０μｇ／Ｌ，２ｈ）处理后，ＰＬＳ中金颗粒的减少极其显著，其金颗粒密度从６６．６５个／μｍ２降至１．７７个／μｍ２，进一步确认该结构上的金颗粒代表ＲＰⅡ转录产物。并且进一步证明该结构是合成ＲＰⅡ转录产物的核内结构。

The pufflike structure (PLS) is an intranuclear structure often observed in cells of higher plants. Several hypotheses regarding the nature of the structure have been put forward while the opinions are still controversial. By using the 5bromouridine5′triphosphate (BrUTP) labelling technique which was developed in early 90s and has been utilized to localize nascent RNA polymeraseⅡ (RPⅡ) transcripts,in combination with immunoelectron microscopy. The authors studied PLSs in the nuclei of the meristematic cells of Allium cepa L. A large number of gold particles were observed over the PLSs of the specimens labelled with BrUTP and antiBrdU antibody,indicating that RPⅡtranscripts were being synthesized actively in the structure. When the specimens were treated with αamanitin (10 μg/L, 2 h) which inhibits the activity of RPⅡ,and followed by treatment with BrUTP and antiBrdU antibody,gold particles in the PLSs of the specimens were decreased dramatically and the gold density of the structure dropped strikingly from 66.65/μm2 to 1.77/μm2, confirming that the gold particles in the structure represented the RPⅡ transcripts. It further demonstrated that the PLS was an intranuclear structure essential for the synthesis of RPⅡtranscripts. 