title: Identification, expression and characterization of rat isoforms of the serum response factor (SRF) coactivator MKL1.
abstract: Megakaryoblastic leukemia 1 (MKL1) is a member of the MKL family of serum response factor (SRF) coactivators. Here we have identified three rat MKL1 transcripts: two are homologues of mouse MKL1 transcripts, full-length MKL1 (FLMKL1) and basic, SAP, and coiled-coil domains (BSAC), the third is a novel transcript, MKL1-elongated derivative of yield (MELODY). These rat MKL1 transcripts are differentially expressed in a wide variety of tissues with highest levels in testis and brain. During brain development, these transcripts display differential patterns of expression. The FLMKL1 transcript encodes two isoforms that utilize distinct translation start sites. The longer form possesses three actin-binding RPXXXEL (RPEL) motifs and the shorter form, MKL1met only has two RPEL motifs. All four rat MKL1 isoforms, FLMKL1, BSAC, MKL1met and MELODY increased SRF-mediated transcription, but not CREB-mediated transcription. Accordingly, the differential expression of MKL1 isoforms may help fine-tune gene expression during brain development.
authors.affiliation: Laboratory of Molecular Neurobiology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Ishikawa
authors.forename: Jun
authors.initials: J
authors.lastname: Shiota
authors.forename: Yuta
authors.initials: Y
authors.lastname: Ishibashi
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Hakamata
authors.forename: Shizuku
authors.initials: S
authors.lastname: Shoji
authors.forename: Mamoru
authors.initials: M
authors.lastname: Fukuchi
authors.forename: Masaaki
authors.initials: M
authors.lastname: Tsuda
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Shirao
authors.forename: Yuko
authors.initials: Y
authors.lastname: Sekino
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Ohtsuka
authors.forename: Jay M
authors.initials: JM
authors.lastname: Baraban
authors.forename: Akiko
authors.initials: A
authors.lastname: Tabuchi
keywords: Alternative promoter; BSAC, basic, SAP, and coiled-coil domains; DAPI, 4′, 6-diamidino-2-phenylindole; GFP, green fluorescent protein; MAL, megakaryocytic acute leukemia; MELODY, MKL1-elongated derivative of yield; MKL1, megakaryoblastic leukemia 1; Megakaryoblastic leukemia; RPEL, arginine proline XXX glutamate leucine; SRF, serum response factor; Serum response factor; Transcript; Transcriptional coactivator