Nucleotide sequence of a highly repetitive component of rat DNA

A highly repetitive component of rat DNA which could not yet be enriched by density gradient centrifugation was isolated with the help of the restriction nuclease Sau3AI. This nuclease converted the bulk of the DNA to small fragments and left a repetitive DNA component as large fragments which were subsequently purified by gel filtration and electrophoresis. This DNA component which was termed rat satellite DNA I is composed of tandemly repeated 370 bp blocks. According to sequence analysis the 370 bp repeats consist of alternating 92 and 93 bp units with homologous but not identical sequences. Methylation of CpG residues was correlated to the rate of cleavage by restriction nucleases. Significant homologies exist between the sequences of rat satellite DNA I and satellite DNAs of several other organisms. The divergence of the sequence of rat satellite DNA I was discussed with respect to evolutionary considerations.