Studies On The Transcription Sites Of RNA Polymerase Ⅲ And Ⅰ And Their Relationships In The Nuclei Of CHO Cells

There are three types of RNA polymerases in eukaryote: polymerase I, II and â…¢. RNA polymerase I synthesizes the three 1 argest rRNAs, 5.8S,18S and 28Sr RNA. RNA polymerase II produces mRNA encoding proteins, and RNA polymerase â…¢ makes 5S rRNA and tRNAs, as well as a few small nuclear RNAs.Since the early 1960s, the transcription sites of these polymerases have been studied by various approaches: autoradiography, immune-electron microscopy and cytochemistry staining. The results of these early research works showed that the localization of RNA polymerase I transcription was in the nucleoli and that of RNA polymerase II and â…¢ in the nucleoplasm. In recent years, more and more experiments indicated that RNA polymerase â…¢ transcription might not occur in the nucleoplasm but in the nucleolus. Nevertheless, there is no direct experimental proof.In this dissertation, the plasmids bearing pol â…¢ recognized promoters were transfected into the CHO cells by electroporation. After fluorescence in situ hybridization, it was showed under the fluorescent microscopy and laser scanning confocal microscopy that RNA polymerase â…¢ transcription occured in the interior and periphery of nucleoli. It was also proofed by the same methods that RNA polymerase I transcription was localized in the nucleoli as stated before. Furthermore, by using two-colored probes to study the relationships between RNA polymerase â…¢ and RNA polymerase I, we observed that the signals of the two RNA polymerase were very close. It is inferred that their transcriptions may occur at the same time.The results will help us to further comprehend the mechanism of RNA polymerase transcription, the way of transcription processing and transportation, and the structural and functional relationship among the three RNA polymerases.