ANCESTRY OF SINE-R.C2 A HUMAN-SPECIFIC RETROPOSON

We have reported previously that a retroposon, containing a variable n umber of tandemly repeated nucleotide sequences, is present in the thi rd intron of the human C2 gene. This element, termed SINE-R.C2, is a m ember of a large retroposon family derived from the endogenous retrovi rus HERV-K10 and estimated to include a few thousand copies per haploi d human genome. In the present study we analyzed genomic DNA from 175 humans from several ethnic groups including Americans of European and African descent, Chinese, Africans, Australians, Pacific Islanders, Ja panese, and Koreans. They all contained SINE-R.C2, as indicated by Sou thern blotting. However, SINE-R.C2 was absent from the genome of nonhu man primates, although SINE-R-type elements were present in chimpanzee s and gorillas and the HERV-K10 genome was apparently present in all p rimates except for New World monkeys. These results indicate that HERV -K10 was inserted into the genome after the divergence of New World mo nkeys; the prototype SINE-R element, after divergence of orangutans; a nd SINE-R.C2, after the split between humans and chimpanzees.