Alternative splicing produces structural and functional changes in CUGBP2

The present study investigated the expression of exon 14, which is an alternatively spliced exon and encodes the first half of the third RRM of CUGBP2. The ratio of exon 14 skipping product (R3δ) to its inclusion was reduced in neuronal cells induced from P19 cells and in the brain. Although full length CUGBP2 and the CUGBP2 R3δ isoforms showed a similar effect on the inclusion of the smooth muscle (SM) exon of the ACTN1 gene, these isoforms showed an opposite effect on the skipping of exon 11 in the insulin receptor gene. In addition, examination of structural changes in these isoforms by molecular dynamics simulation and NMR spectrometry suggested that the third RRM of R3δ isoform was flexible and did not form an RRM structure.Our results suggest that CUGBP2 regulates the splicing of ACTN1 and insulin receptor by different mechanisms. Alternative splicing of CUGBP2 exon 14 contributes to the regulation of the splicing of the insulin receptor. The present findings specifically show how alternative splicing events that result in three-dimensional structural changes in CUGBP2 can lead to changes in its biological activity.The CELF (CUGBP and ETR-3 Like Factor)/Bruno-like protein family plays important roles in the regulation of alternative splicing and translation [1-5]. In mammals, the CELF/Bruno-like family includes six members and is classified into two subgroups based on overall sequence similarity. One group is composed of CUGBP1 and CUGBP2, which share 76% amino acid sequence identity [6]. The other group contains BRUNOL1 (CELF3), BRUNOL5 (CELF5), BRUNOL6 (CELF6), and CELF4, which share 62-66% a.a. sequence identity with each other and 44% sequence identity with CUGBP1 [6]. CELF proteins have two consecutive RNA recognition motifs (RRMs) (RRM1-2) in the N-terminal region and another RRM (RRM3) in the C-terminal region. RRM2 and RRM3 are separated by a linker region that consists of 160-230 amino acids. CELF family members are expressed in multiple tissues with