Organization and chromosomal distribution of a novel repetitive DNA component from Muntiacus muntjak vaginalis with a repeat length of more than 40 kb

The organization and chromosomal distribution of the repetitive DNA component IB from Muntiacus muntjak vaginalis (MMV) was investigated. DNA fragments of component IB were cloned in cosmids and their structure analysed using restriction nucleases and blot-hybridization experiments. Two cosmids were found to be practically identical by restriction enzyme mapping. The repeat unit of component IB DNA is more than 40 kb and contains the 11 and 18 kb Bam HI fragments, which have previously been shown to cross-hybridize with MMV satellite IA. In addition, the repeat unit contains long stretches of DNA sequences which are unique to component IB. In situ hybridization experiments showed that component IB has the properties characteristic of long interspersed repetitive DNA rather than tandemly repeated satellite DNA. Consistent with this conclusion, only a minor fraction of component IB is located on the X chromosome as demonstrated by the analysis of somatic cell hybrids. This is in marked contrast to satellite IA that is specific for the X chromosome. These results have interesting implications for the evolution of the component I DNA family of the MMV genome.