Autonomous replicating sequences from intron of human ras gene in a simian virus 40 T antigen dependent system.

Of the several DNA fragments present in the human lung cancer gene, 1.1 and 2.0 kilobase (kb) fragments corresponding to the intron of this gene were hybridized to a half part of the 27 nucleotides perfect palindrome present in the initiation part of replication in simian virus 40 (SV40) DNA. These two fragments cloned in pBR322 had good template activity, and the initiation of DNA replication started from the region of these fragments in an in vitro system, in which the initiation of DNA replication occurs on cloned DNA containing SV40 origin of DNA replication as described previously. Furthermore, these two clones could replicate autonomously in nuclei of SV40 transformed Cos cells, producing SV40 T antigen constitutively when the clones were transfected into Cos cells. These results show that functional SV40 origin-like sequences are present in human genomes, and they can replicate autonomously within the cells which are producing SV40 T antigen.