Hideaway, a repeated element from Ascobolus immersus is rDNA-associated and may resemble a retrotransposon

A lambda library of Ascobolus immersus stock 50 was screened for repeated D NA sequences by employing differential hybridization to identify transposab le elements. Several lambda clones carrying repeated DNA sequences were obt ained. One clone contains a repeated DNA sequence with unusual characterist ics. This DNA element appears to be associated with rDNA sequences. Its met hylation pattern is also reminiscent of rDNA. Sequence analysis indicates t hat all or at least many copies of the element have integrated in the exter nal spacer sequence separating the rDNA repeats, possibly to avoid complete inactivation by methylation. The element has been named "Hideaway". It pos sesses structural characteristics of class I retrotransposons, most notably the presence of long direct repeats. The data presented here are discussed with respect to the ability of repeated DNA sequences to escape host defen se mechanisms.