A new rodent short retroposon B1-dID

Copies of an unusual retroposon were isolated from the genomes of forest do rmouse (Dryomys nitedula), long-tailed marmot (Marmota caudata), and palm s quirrel (Menetes berdmorei). Similarly to the primate Alu element, it consi sts of two monomers, but by contrast to Alu only its left B1-like monomer d escends from 7SL RNA, while the right one is similar to the rodent tRNA-rel ated ID retroposon. Several structural variants of this new retroposon (B1- dID) were recognized; some of them were found in the genomes of beavers (Ca storidae) and sparsely in guinea pig (Caviidae) and porcupine (Hystricidae) . Evolution of these retroposons and rodents is discussed on the basis of n ucleotide sequence analysis.