Progress in visualization of eukaryotic gene transcription.

Methods for visualization of the ultrastructure of transcriptionally active eukaryotic genes have been developed using chromatin from giant nuclei of amphibian oocytes (Miller and Beatty 1969). Rapidly isolated chromatin is subjected to low salt treatment in order to dissociate most chromatin associated proteins. As a result, gene-chromatin with associated RNA polymerase particles and RNA transcripts can be directly analysed in electron microscope chromatin spread preparations. More recently, progress has been made in utilising living amphibian oocyte nuclei as a transcription system for cloned eukaryotic genes. In this article, an account of such experiments is given, with emphasis on results and problems of chromatin and transcription organization of microinjected cloned genes. The described transcription assay system possesses important potential for investigation of gene mutations and in particular for the elucidation of molecular aspects of experimental oncology and molecular human genetics.