Identification of regulatory cis-acting elements for alternative splicing of presenilin 2 exon 5 under hypoxic stress conditions.

An alternatively spliced form of the presenilin 2 (PS2) gene lacking exon 5 (PS2V) was found in human brains with sporadic Alzheimer's disease. PS2V was induced by hypoxic stress in human neuroblastoma SK-N-SH cells, indicating that hypoxic stress affects the splicing machineries for PS2 exon 5. Here, we identified the critical cis-acting element (sec 2) on the PS2 pre-mRNA responsible for the aberrant splicing of PS2 exon 5 under hypoxic stress conditions. The element was composed of 23 nucleotides in exon 5 and RNA structural analyses showed a stem-loop structure in this sequence. Treatment with an antisense oligonucleotide directed toward the cis-acting element caused an increase in exon 5 inclusion. These results indicate that the sec 2 identified in this study is a novel regulatory element for exon 5 splicing under stress conditions and that trans-acting factors could specifically bind to the element to skip exon 5 of PS2.