The Studies On Dynamic Relationship Between HeLa Nucleolar RDNA Transcription, Pre-rRNA Processing And The Ultrastructure

Nucleolus is one of the prominent nuclear structures in eukaryotic cell and the two subunits of ribosome are made in it, which are the factories of synthesizing protein in cell. Nucleolus is mainly consisted of FC, DFC and GC. It is found in the cells of animal and plant and yeast and there is more than one nucleolus in one nucleus. Nucleolus is dismissed in prophase and reformed in telephase in cell cycle. The nucleolus has been studied for a long time but there have been still many arguments about nucleolar structures and function. Of which, there were different results on the size and its changes of FC and DFC during G1 (G0) and G2 phases. Still there were different reports concerning the sites of nucleolar transcription and processing. The different results were even appeared in the results of the studies with same material and with same ways. The reasons of different results concerning nucleolar structure and its function might be in being short of all-round and systematic studies for the dynamic changes about nucleolus during interphase.In this study, HeLa cell was used as an experiment material. By using conventional transmission electronmicroscope, cytochemistry, immunoelectron microscope techniques and in situ hybridization, we studiedâ‘ the ultrastructure of nucleolus of HeLa cell in G1, S and G2 phases and its changes;â‘¡the distribution of DNA in the nucleolus and its changes during interphase;â‘¢the sites of rRNA transcription and its changes;â‘£the sites of pre-rRNA processing and its changes in the three phases of interphase. The results showed that the structure and its function underwent dynamic changes during interphase:1,The results of using conventional electromicroscope techniques showed that it was different for the ultrastructures of HeLa cell during interphase. In G1 phase, there were a few small nucleoli begun to fuse into big one and then as did the FCs in the big nucleolus fused. Sec-FC and sec-DFC were derived from the parts between pri-FC and pri-DFC in S phase and both of pri-FC and sec-DFC were coexisted in reticulated nucleolus in G2 phase. The present work firstly showed that there were a process of sec-FC and sec-DFC deriving from pre-FC and pre-DFC.2,In the results of using NAMA-Ur methods, DNA in the pre-FC was well-distributed in a shape of ring formed in G1 phase and dismissed in G2 phase. DNA was not well-distributed in DFC and the fibres of rDNA were distributed in the form of a wheel spoke next to the edge of the FC. The process of derivation of sec-FC occurred in the DNA between pre-FC and pre-DFC. When chromatin was condensed in late of G2, the chromatin around the nucleolus was slowly dismissed and the shape of the nucleolus was changed into the lost with the nucleolus associated chromatin being dismissed.