MOLECULAR ANALYSIS OF ABNORMAL SATELLITE-I DNA FROM A BUF MNA RAT THYMOMA/

BUF/Mna rats develop spontaneous thymomas in an autosomal dominant man ner. We constructed recombinant plasmid library of 90 and 185 base-pai red (bp) satellite I DNA fragments isolated from BUF/Mna rat thymoma D NA. Four unusual clones containing 93, 95, 95, and 173 bp inserts were isolated by colony hybridization with Wistar rat satellite I DNA. Nuc leotide sequence analysis of the inserts of the 4 clones revealed abno rmal sequence organization and unusual subunit structure of the rat sa tellite I DNA. Sequence comparisons between normal and abnormal satell ite I DNA suggested that the unusual subunit structure could be genera ted by the change of the Hinf I recognition sequence to an Eco RI clea vage site, in addition to random deletions, insertions and base substi tutions. The heptanucleotide sequence TGGGAAC, which is strictly conse rved in normal subunits, was completely lost in all these clones. Sout hern blot hybridization revealed the amplification of abnormal satelli te I DNA in BUF/Mna rat thymomas.