SR proteins regulate V6 exon splicing of CD44 pre-mRNA

CD44 pre-mRNA includes 20 exons, of which exons 1-5 (C -C ) and exons 16-20 (C -C ) are constant exons, whereas exons 6-15 (V -V ) are variant exons. V -exon-containing isoforms have been known to be implicated in tumor cell invasion and metastasis. In the present study, we performed a SR protein screen for CD44 V splicing using overexpression and lentivirus-mediated shRNA treatment. Using a CD44 V minigene, we demonstrate that increased SRSF3 and SRSF4 expression do not affect V splicing, but increased expression of SRSF1, SRSF6 and SRSF9 significantly inhibit V splicing. In addition, using a constitutive exon-specific primer set, we could not detect alterations of CD44 splicing after SR protein-targeting shRNA treatment. However, using a V specific primer, we identified that reduced SRSF2 expression significantly reduced the V isoform, but increased V and V isoforms. Our results indicate that SR proteins are important regulatory proteins for CD44 V splicing. [BMB Reports 2016; 49(11): 612-616].