SV40 DNA sequences as an example of the structure of genes functioning in animal cell nuclei

Recent studies of the structure of messenger RNA have demonstrated the existence of untranslated sequences of the 3' and 5' end of the messages. In addition analysis of transcription in vitro has indicated that the nucleotide sequence U6 purine may be part of a transcription termination signal in prokaryotes. Recently it has been possible to determine the sequence of extensive portions of the DNA of SV40 virus. This article reviews the analogies between certain of these sequences and sequences available from prokaryotic messengers and DNAs. Unusual structures, including blocks of AT-rich and GC-rich segment sections and symmetric regions in the DNA near the origin of DNA replication, have been demonstrated and the distribution of stretches of 6 or more deoxyadenylic acids in the DNA of SV40 is consistent with some rho for these sequences in animal cells, either as terminators of transcription or as sites where degradation of transcripts is initiated or sites related to the selective rejection or degradation of transcipts.