Takeo K, Kawai T, Nishida K, Masuda K, Teshima-Kondo S, Tanahashi T, Rokutan K. Oxidative stress-induced alternative splicing of transformer 2 beta (SFRS10) and CD44 pre-mRNAs in gastric epithelial cells. Am J Physiol Cell Physiol 297: C330-C338, 2009. First published May 13, 2009; doi: 10.1152/ajpcell.00009.2009.-The tra2 beta gene encoding an alternative splicing regulator, transformer 2-beta (Tra2 beta), generates five alternative splice variant transcripts (tra2 beta 1-5). Functionally active, full-length Tra2 beta is encoded by tra2 beta 1 isoform. Expression and physiological significance of the other isoforms, particularly tra2 beta 4, are not fully understood. Rat gastric mucosa constitutively expressed tra2 beta 1 isoform and specifically generated tra2 beta 4 isoform that includes premature termination codon-containing exon 2, when exposed to restraint and water immersion stress. Treatment of a gastric cancer cell line (AGS) with arsenite (100 mu M) preferentially generated tra2 beta 4 isoform and caused translocation of Tra2 beta from the nucleus to the cytoplasm in association with enhanced phosphorylation during the initial 4-6 h (acute phase). Following the acute phase, AGS cells continued upregulated tra2 beta 1 mRNA expression, and higher amounts of Tra2 beta were reaccumulated in their nuclei. Treatment with small interference RNAs targeting up-frameshift-1 or transfection of a plasmid containing tra2 beta 1 cDNA did not induce tra2 beta 4 isoform expression and did not modify the arsenite-induced expression of this isoform, suggesting that neither the nonsense-mediated mRNA decay nor the autoregulatory control by excess amounts of Tra2 beta participated in the tra2 beta 4 isoform generation. Knockdown of Tra2 beta facilitated skipping of the central variable region of the CD44 gene and suppressed cell growth. In contrast, overexpression of Tra2 beta stimulated combinatorial inclusion of multiple variable exons in the region and cell growth. The similar skipping and inclusion of the variable region were observed in arsenite-treated cells. Our results suggest that Tra2 beta may regulate cellular oxidative response by changing alternative splicing of distinct genes including CD44.
