Baculovirus expression system cells expressing v-myb oncogene: The distribution of RNA and DNA in specific nuclear compartments with respect to structures interacting with anti-v-Myb antibody.

The distribution of RNA, total DNA and newly synthesized DNA within nucleol i-like structures in insect cells overexpressing v-myb oncogene was investi gated. Three types of these structures which revealed interaction with anti -v-Myb oncoprotein antibody were found at the ultrastructural level. Specif ic staining by toluidine blue at pH 5.2 showed the presence of RNA in these nucleoli-like structures. To detect total DNA, the in situ terminal deoxyn ucleotidyl transferase-immunogold technique was used. In addition to an exp ected labeling of host condensed chromatin, the labeling of the three types of nucleoli-like structures differed from each other. While the compact (t ype I) and ring-shaped (type II) nucleoli-like structures were labeled only on their periphery and in the proximity of baculovirus particles that inte racted with them, the structures with an appearance of nucleolonemas (type III) were labeled strongly. Incorporation of 5-bromo-2-deoxyuridine, in spi te of a poor labeling of newly synthesized DNA, confirmed these results. We suggest that the nucleoli-like structures of type I and II are of nucleola r origin. The type III more likely represents virogenic stroma or viral DNA storage site.