| Summary: | <p>Abstract</p> <p>Background</p> <p>Overlapping sense/antisense genes orientated in a tail-to-tail manner, often involving only the 3'UTRs, form the majority of gene pairs in mammalian genomes and can lead to the formation of double-stranded RNA that triggers the destruction of homologous mRNAs. Overlapping polyadenylation signal sequences have not been described previously.</p> <p>Results</p> <p>An instance of gene overlap has been found involving a shared single functional polyadenylation site. The genes involved are the human alpha/beta hydrolase domain containing gene 1 (<it>ABHD1</it>) and <it>Sec12</it> genes. The nine exon human <it>ABHD1</it> gene is located on chromosome 2p23.3 and encodes a 405-residue protein containing a catalytic triad analogous to that present in serine proteases. The Sec12 protein promotes efficient guanine nucleotide exchange on the Sar1 GTPase in the ER. Their sequences overlap for 42 bp in the 3'UTR in an antisense manner. Analysis by 3' RACE identified a single functional polyadenylation site, ATTAAA, within the 3'UTR of <it>ABHD1</it> and a single polyadenylation signal, AATAAA, within the 3'UTR of <it>Sec12</it>. These polyadenylation signals overlap, sharing three bp. They are also conserved in mouse and rat. <it>ABHD1</it> was expressed in all tissues and cells examined, but levels of <it>ABHD1</it> varied greatly, being high in skeletal muscle and testis and low in spleen and fibroblasts.</p> <p>Conclusions</p> <p>Mammalian <it>ABHD1</it> and <it>Sec12</it> genes contain a conserved 42 bp overlap in their 3'UTR, and share a conserved TTTATTAAA/TTTAATAAA sequence that serves as a polyadenylation signal for both genes. No inverse correlation between the respective levels of <it>ABHD1</it> and <it>Sec12</it> RNA was found to indicate that any RNA interference occurred.</p>
|
|---|
