Evidence for rolling-circle replication in a major satellite DNA from the South American rodents of the genus Ctenomys

Abstract

A major Pvu II satellite DNA has been cloned from a South American octodontid rodent of the genus Ctenomys (C. porteousi). The satellite monomer, termed RPCS, is 337 bp in size and 42% G+C. Analysis of the nucleotide sequence demonstrates that RPCS is not composed of a series of shorter repeats. RPCS-rclated sequences were found in II of 12 Ctenomys species analyzed by hybridization under high-stringency conditions. The only negative species, C. opimus. was reactive under low-stringency conditions. RPCS-related sequences were not found under high- or low-stringency conditions in Calomys musculinus and Mas musculus. However, under low-stringency conditions, RPCS-related sequences were found in the octodontid Octodontomys gliroides, which is thought to have diverged from the genus Ctenomys more than 10 Myr ago. The pattern of periodicities observed, by restriction analysis, between Ctenomys species in the satellite array can be mainly accounted for by a rolling-circle amplification mechanism but cannot be solely accounted for by unequal crossing-over.