Figure 3.

Human TREX2 isoforms. (A) Genomic structure of the human TREX2 gene. Human TREX2, located on chromosome X, contains 16 exons (26), of which only exons 15 and 16 are shown. TREX2^L1 (NP_542431) is a spliced product of exons 15 and 16. TREX2^L2 is a novel spliced product of exons 15, 15b and 16. The nucleotide sequence for TREX2^L2 has been deposited in the GenBank database under accession number DQ650792. The amino acid sequence of TREX2^L2 can be accessed through NCBI Protein Database under NCBI access number ABG43103. Oval indicates the predicated promoter region. (B) Protein sequence alignment of three TREX2 isoforms. TREX2^L1 encodes a 279-amino-acid peptide and TREX2^L2 is a 278-amino-acid peptide. Both TREX2^L1 and TREX2^L2 have a predicated molecular weight of ∼30 kDa. Red depicts identical homology among the three TREX2 isoforms; blue depicts identical homology between the two longer isoforms; black dots show the difference between the two longer isoforms. (C) Semi-quantitative RT-PCR to detect the TREX2 isoforms in cancer-derived human cells (HeLa, HCT116, LoVo, PC3 and BG1) and human kidney. The TREX2^L1 isoform (upper panel) is amplified with primers hTX2L1F (half arrow in the yellow exon) and hTX2R (white half arrow in the red exon). As a control, hTX2short (black half arrow in the red exon) and hTX2R were used to amplify the product common to all isoforms (lower panel). These products were re-amplified with the same forward primer and a new internal primer, hTX2Ri (green half arrow in the red exon). This TREX2^L1 product was sequenced to verify the results. We used hTX2L2F (half arrow in the orange exon) and hTX2R in our attempt to amplify the TREX2^L2 isoform; however, no product was seen. PCR was performed with different concentrations of cDNA (μg).