Structural and functional characterization of the human gene for sorting nexin 1 (SNX1)

The aim of the present study was to identify the gene for sorting nexin 1 (SNX1) to evaluate the potential for tissue-specific alternative splicing and to analyze the activity of the SNX1 promoter. The coding DNA for SNX1 was divided between 15 exons in 43 kb of genomic DNA located on human chromosome 15q22. Although SNX1 mRNA expression was widespread in human tissues, alternative splicing is thought to generate skipped exons in SNX1 cDNAs. By determination of the SNX1 gene structure and an analysis of the mRNAs in a variety of tissues using RT-PCR, we demonstrated that SNX1 mRNAs are alternatively spliced. Exon-skipped products were less abundant than full-length SNX1 mRNA species, but the ratio of skipped to full-length mRNA indicated that alternative splicing may be developmentally regulated in the liver. Consistent with widespread mRNA expression, the SNX1 promoter was GC rich and lacked a TATA box, features characteristic of housekeeping promoters. The promoter activity was dependent on the presence of proximal sequences that contained initiator elements and predicted binding sites for the transcription factors Sp1 and E2F. These findings indicate that regulation of SNX1 gene expression at the transcriptional level is likely minor. Rather, developmentally specific exon skipping provides a potential mechanism for regulating the activity of SNX1.