TheKLHLI-antisense transcript (KLHLIAS) is evolutionarily conserved

Abstract

Spinocerebellar ataxia type 8 (SCA8) is caused by a CTG expansion in an untranslated, endogenous antisense RNA that overlaps theKelch-like I (KLHLI) gene. The normal function of this transcript is currently unknown. We have now identified the promoter region for theKLHL1-antisense (KLHLIAS) RNA and report that aKlhl1as transcript is present in the mouse as well. Human and mouseKlhl1AS are transcribed from homologous promoter regions in the first intron ofKLHLI and extend through the transcription and translation start sites as well as the first splice donor sequence ofKLHL1. We found that the mouseKlhlIas RNA is not spliced and terminates in a polyadenylation site in theKlhlI promoter region, whereas both the present and previous work show that humanKLHLIAS is highly variably spliced into processed transcripts that contain up to six exons. MouseKlhlIas transcript was detected in RNA isolated from the cerebellum and from total adult brain and total fetal tissue, and at a low level in testis and ovary. Similarly, humanKLHL1AS is expressed in various brain tissues, including the cerebellum, the tissue most affected by SCA8, and was detected at low levels in testis and kidney. The evolutionary conservation of this antisense/sense transcriptional organization strongly indicates thatKLHLIAS transcripts play a significant biological role in both human and mouse, presumably as a regulator ofKLHLI expression.