Electron microscopic autoradiographic study of RNA synthesis in yeast nucleus

Abstract

High resolution autoradiography of isolated yeast nuclei has been used to investigate the distribution of newly formed RNA in the nucleus. The nuclei were isolated after incubation of spheroplasts with 3H-uracil for 5 min. Most grains (80%) are located over the dense crescent. In the dense crescent the grains seem to be associated with the nucleolonema. An analysis of the nuclear RNA on polyacrylamide gels shows that the incorporated 3H-uracil is predominantly present in the initial (37S) ribosomal precursor RNA. The EM autoradiographic and biochemical data, taken together, strongly suggest that we have to ascribe a nucleolar function to the dense crescent of the yeast nucleus.