FIGURE 1.

Genomic structure and heterologous expression of human MGRN1 isoforms. A, genomic structure of human MGRN1 indicating exons (numbered boxes) and introns (lines) and scheme of MGRN1 protein isoforms generated by alternative splicing of exons 12 and 17. (+)- and (−)-forms contain or lack exon 12, respectively. L and S isoforms possess a long or shorter exon 17 generated by the use of an alternative exon junction. RF, C3HC4 RING finger domain (residues 278–316 encoded by exon 10). The peptide sequence encoded by exon 12, containing a bipartite nuclear localization signal highlighted with bold characters, is shown. B, Myc epitope-tagged MGRN1 isoforms were transfected in HEK293T cells and HA epitope-labeled forms were used in melanoma cells. MGRN1 expression was compared by Western blot. Cells transfected with empty vector (lanes labeled pcDNA) are shown as controls for specificity. For HEK cells, endogenous Myc provided an internal loading control. For HBL cells, blots were stripped and stained for ERK2 as loading control (not shown). C, confocal microscopy of HEK293T cells expressing Myc epitope-tagged MGRN1 isoforms. Transfected cells were fixed, permeabilized, and stained with αMyc.