Activation of SV40 DNA replication in vivo by amplification-promoting sequences of the mouse ribosomal gene cluster

Abstract. 

Mouse genomic DNA sequences from the region upstream of the ribosomal genes reported to contain amplification-promoting activity (APS1 and APS2) were tested for their ability to support SV40 replication in vivo. Both APSs can functionally replace the auxiliary sequence 2 on the late side of the SV40 origin, which facilitates initiation of replication. This stimulatory activity on the SV40 origin was orientation independent and was exerted over a distance of at least 0.9 kb. However, the APS2 element can not substitute for the auxiliary sequence 1 on the early side of the origin. Although both APS elements contain various prospective transcription factor binding sites, they do not trans-activate transcription from a minimal promoter. In this respect they differ from the enhancer element of the auxiliary sequence 2 of the SV40 origin. These results suggest that the rDNA sequences tested contain genetic information facilitating replication initiation on a viral core origin.