1Kunihiko Takamatsu, 2Mizuki Takahashi, 1Katsuhiko Murakami, 1Atsushi Toyoda, 1D.Taylor Todd, 1Yoko Kuroki, 3Asao Fujiyama, 4Masahira Hattori, 1Tadayuki Takeda, 1Yoshiyuki Sakaki
1RIKEN Genomic Science Center, Japan, 2Tokyo Institute of Technology, Japan, 3National Institute of Informatics, Japan, 4Kitasato University, Japan
DSCR9 on human chromosome 21 emerged during evolution as a new class of gene in the primate lineage (Takamatsu K et al, DNS Res. 2002 9 89-97). In the last meeting, we reported nucleotide sequences of the 5' flanking and 'exon' regions of DSCR9 in various primate genomes including anthropoids (gorilla and orangutan), old world monkeys (crab-eating macaque, African green monkey and Japanese macaque), and new world monkeys (spider monkey and marmoset) and demonstrated that the base substitution rate of the 5' flanking region is lower than that of the 'exon' regions. From these observations we suggested that DSCR9 may encode a non-coding RNA rather than protein. Also, we found a LTR sequence in the 5' flanking region which may be involved in the transcriptional activities of DSCR9.
In this meeting we will report additional comparative analysis using prosimian genome (lemur) which diverged from human ancestor around 50 million years to investigate the origin of DSCR9. A BAC clone of lemur genome DNA corresponding to DSCR9 was isolated from lemur BAC libraries. The data show that there exists some similarity between human and lemur but most interestingly there is no LTR counterpart in lemur genome suggesting that the LTR was inserted in between prosimian and new world monkeys. Based on these observations the origin and evolution of DSCR9 will be discussed.
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