Replication but not transcription of simian virus 40 DNA is dependent on nuclear domain 10

DNA viruses from several families including herpes simplex virus type 1, ad enovirus type 5, and simian virus 40 (SV40), start their transcription and replication adjacent to a specific nuclear domain, ND10. We asked whether a specific viral DNA sequence determines the location of these synthetic act ivities at such restricted nuclear sites. Partial and overlapping SV40 sequ ences were introduced into a beta-galactosidase expression vector, and the beta-galactosidase transcripts were localized by in situ hybridization, Tra nscripts derived from control plasmids were found throughout the nucleus an d at highly concentrated sites but not at ND10. SV40 genomic segments suppo rted ND10-associated transcription only when the origin and the coding sequ ence for the large T antigen were present. When the large T-antigen coding sequence was eliminated but the T antigen was constitutively expressed in C OS-7 cells, the viral origin was sufficient to localize transcription and r eplication to ND10. Deletion analysis showed that only the large T-antigen binding site II (the core origin) was required but the T antigen was needed for detectable transcription at ND10. Large T antigen expressed from plasm ids without the viral core origin did not bind or localize to ND10. Blockin g of DNA replication prevented the accumulation of transcripts at ND10, ind icating that only sites with replicating templates accumulated transcripts. Transcription at ND10 did not enhance total protein synthesis of plasmid t ranscripts. These findings suggest that viral transcription at ND10 may onl y be a consequence of viral genomes directed to ND10 for replication. Altho ugh plasmid transcription can take place anywhere in the nucleus, T-antigen -directed replication is apparently restricted to ND10.