Studies On The Localizations Of RNA Polymerase Ⅰand Ⅲ Transcription In The Nuclei Of HeLa Cells

There are three types of RNA polymerases in eukaryotic cells: polymerase I, â…¡ and â…¢. They perform different functions in the cells. RNA polymerase I synthesizes three largest rRNAs, 5.8S, 18S and 28S rRNA. RNA polymerase â…¡ produces mRNA encoding protein, and RNA polymerase â…¢ makes 5S rRNA and tRNA, as well as a few small nuclear RNAs.The transcription localizations of these polymerases have been studied since early 1960s. The results of these early research works showed that the transcription of RNA polymerase I was localized in the nucleoli while that of RNA polymerase â…¢ in the nucleoplasm. However, with the development and the application of new techniques, the reliability of the methods used in the research of the transcription site of RNA polymerase I was doubted; and also, some indirect results indicated that the transcription of RNA polymerase â…¢ might occur in the nucleoli. But there is no direct experimental proof. In fact, an alternate method to identify directly the precise transcription sites of RNA polymerase I and â…¢ would also be desirable.In this dissertation, the plasmids bearing RNA polymerase I and â…¢ promoter were transfected into HeLa cells, respectively. After being detected by fluorescence in situ h ybridization t o D NA a nd R NA level, i t w as s howed u nder t he 1 aser s canning confocal microscopy that the localizations of RNA polymerase I were in the nucleoli; Those of RNA polymerase â…¢ were in the nucleoli and its periphery regions, but not in the nucleoplasm.The results will help us to comprehend the mechanism of RNA polymerase transcription, the way of transcription processing and transportation, and the structural and functional relationship among three RNA polymerases.