The 81st Annual Meeting of the Genetic Society of Japan
Faculty of Science, Shinshu University
September 17, 2009
Invited presentation

Retrotransposition as a source of new promoters
Kohji Okamura1 and Kenta Nakai1,2
1Hum. Genome Ctr., Inst. Med. Sci., Univ. Tokyo, Japan, 2BIRD, JST, Japan
Retrotranspositions of functional genes have been believed to give rise to processed pseudogenes. However, recent studies demonstrated that some retrotransposed genes are transcriptionally active. Because promoters are not thought to be retrotransposed along with exonic sequences, these active genes must have acquired a working promoter by mechanisms that are yet to be determined. Hence, comparison between a retrotransposed gene and its source gene appears to provide a unique opportunity to investigate the promoter creation. Here, we identified 29 gene pairs in the human genome, consisting of a functional retrotransposed gene and its parental gene, and compared their respective promoters. In more than half of these cases, we unexpectedly found that a large part of the promoter had been transcribed, reverse transcribed, and then integrated to be operative at the transposed locus. This observation can be ascribed to the recent discovery that transcription start sites tend to be interspersed rather than situated at one specific site. This propensity could confer retrotransposability to promoters per se.