The role of antisense RNA Ube3a-ATS in Ube3a imprinting and Angelman syndrome
Angelman syndrome is caused by deficiency of UBE3A. Unlike ordinary autosomal genes, it is subject to genomic imprinting with expression only from maternal chromosome. It is unknown how such imprinted status is established, since no differential DNA methylation was found to be associated with the UBE3A locus. On the other hand, an antisense non-coding RNA named UBE3A-ATS overlapping UBE3A locus was identified with mono-allelic expression from paternal chromosome. Extensive negative association between Ube3a-ATS and Ube3a was reported from both mice and human studies. In this proposal, we hypothesize that Ube3a-ATS directly mediates paternal Ube3a silencing by inhibiting its transcription elongation. To test this, we have generated a mouse model with truncated Ube3a-ATS expression. Studying of this mouse model will reveal the role of Ube3a-ATS in Ube3a imprinting and Angelman syndrome. Binding of transcription initiation complex to Ube3a promoter was found to be equal on both paternal and maternal chromosomes. To test if paternal Ube3a silencing is caused by failure of transcription elongation, nascent RNAs immunoprecipitated (RNA-IP) with RNA polymerase II will be analyzed. Finally, profiles of histone modifications of Ube3a will be studied by ChIP (chromatin-immunoprecipitation)-chip, to further expand our knowledge about Ube3a imprinting. Overall, we propose to study the role of antisense RNA Ube3a-ATS in Ube3a imprinting and their interaction using mouse models. UBE3A-ATS may be developed as new therapeutic target for inactivation in Angelman syndrome to reactivate silenced paternal UBE3A, and our research will provide unique insight into the relevant regulatory mechanisms.