Artiodactyl retroposons: association with microsatellites and use in SINEmorph detection by PCR

During a search of polymorphic microsatellites for bovine genome mapping, we found that microsatellites often occur as tails of artiodactyl C-A retroposon elements. In this element, C (85bp) is a tRNA derivative, while A (117bp) is of unknown origin. The A element also occurs as dimer element with a connecting 27bp linker sequence comprising hexanucleotide CACTTT repeats. In 10 clones (45% of those selected deliberately for dinucleotide repeats), the microsatellite motif is associated with the C-A retroposon. In 50% of 44 database artiodactyl C-A sequences, the element also has a microsatellite tail. The microsatellite is usually a simple (CA)n repeat, but in some cases it is an apparent derivative of the linker sequence CACTTT. All but one of 33 database dimer elements have trinucleotide repeat tails (AGC)n, n = 1-9. Microsatellites, retroposons, and their truncated versions (C and/or A) often occur as clusters. We derived the consensus sequence (202bp) of the C-A element, and designed four primers for inter-SINE amplification with the aim of finding SINEmorph polymorphisms. The method is potentially powerful for rapidly producing polymorphic markers for artiodactyl genome mapping.