Occurrence of reiterated sequences in an untranslated region of Simian virus 40 DNA determined by nucleotide sequence analysis.

An earlier report (Subramanian, Dhar, and Weissman, 1977c) presented the nucleotide sequence of Eco RII-G fragment of SV40 DNA, which contains the origin of DNA replication. The nucleotide sequence of Eco RII-N fragment located next to Eco RII-G on the physical map of SV40 DNA is presented in this report. Eco RII-N is found to be a tandem duplication of the last 55 nucleotides of Eco RII-G. This tandem repeat is immediately preceded by two other reiterated sequences occurring within Eco RII-G, one of them being a tandem repeat of 21 nucleotides and the other a nontandem repeat of 10 nucleotides. These repetitive sequences occur in close proximity to the origin of DNA replication which is known to contain other specialized sequences such as a few palindromes (one of which is 27 long and possesses a perfect 2-fold axis of symmetry), one "true" palindrome, and a long A/T-rich cluster. The repeats (and the replication origin) occur within an untranslated region of SV40 DNA flanked by (the few) structural genes coding for the "late" proteins on the one side and that (those) coding for the "early" protein(s) on the other side. The reiterated sequences are comparable in some respects to repetitive sequences occurring in eucaryotic DNAs. Possible biological functions of the repeats are discussed.