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. 2021 Nov 2;14:767842. doi: 10.3389/fnmol.2021.767842

Figure 1.

Figure 1

Structures of MKL/MRTF isoforms. MKL/MRTF contains RPEL motifs, a basic region (B1, B2, or B3), polyglutamine repeat (polyQ), SAF-A/B, Acinus, PIAS domain (SAP), leucine zipper domain (LZ), and transcriptional activation domain (TAD). Domains and their functions were illustrated using the article Kalita et al. (2012) as a reference. (A) Structures of rat MKL1/MRTFA isoforms and variation of the N-termini of isoforms modified from Ishikawa et al. (2013). Full-length MKL1 has two translational start sites, giving rise to FLMKL1 with three RPEL motifs and MKL1met with two RPEL motifs. FLMKL1, BSAC, and MELODY have individual 5′ exons and their N-terminal regions differ. (B) Structures of mouse MKL2/MRTFB isoforms and variation of the N-termini of isoforms modified from Ishibashi et al. (2020). Isoforms 1, 2, and 3 have individual 5′ exons, isoform 3 and SOLOIST/MRTFB i4 have the same 5′ exons. The difference between isoform 3 and SOLOIST/MRTFB i4 is a microexon encoding 21 amino acid residues, which disrupts the ERK-docking motif of isoform 3. SRF, serum response factor; MRTF, myocardin-related transcription factor; MKL, megakaryoblastic leukemia; BSAC, basic, SAP, and coiled-coil domain; MELODY, MKL1-elongated derivative of yield; FLMKL1, Full-length MKL1; SOLOIST, spliced neuronal long isoform of SRF transcriptional coactivator; RPEL, RPXXXEL; ERK, extracellular signal regulated kinase.