Simian virus 40 tandem repeated sequences as an element of the early promoter.

On the late side of the simian virus 40 (SV40) DNA replication origin are several sets of tandem repeated sequences, the largest of which is 72 base pairs long. The role of these sequences was examined through construction of deletion mutants of SV40. A mutant from which one of the 72-base-pair repeated units was removed is viable upon transfection of monkey kidney cells with viral DNA. Extension of this deletion into the second repeated unit, however, leads to nonviability, as recognized by the absence of early transcription and of tumor antigen production. These observations indicate that the 72-base-pair repeated sequences form an essential element in the early viral transcriptional promoter and explain the inability of such a deleted genome to complement an early temperature-sensitive mutant of SV40, tsA, as well as the failure to replicate its DNA. In a parallel experiment it was found that the extended deletion mutant was also unable to complement a late temperature-sensitive mutant of SV40, tsB. This suggests that the extended mutant is also defective in DNA replication or late transcription (or both).