Differentiation and fiber type-specific activity of a muscle creatine kinase intronic enhancer

Abstract

BackgroundHundreds of genes, including muscle creatine kinase (MCK), are differentially expressed in fast- and slow-twitch muscle fibers, but the fiber type-specific regulatory mechanisms are not well understood.ResultsModulatory region 1 (MR1) is a 1-kb regulatory region within MCK intron 1 that is highly active in terminally differentiating skeletal myocytes in vitro. A MCK small intronic enhancer (MCK-SIE) containing a paired E-box/myocyte enhancer factor 2 (MEF2) regulatory motif resides within MR1. The SIE's transcriptional activity equals that of the extensively characterized 206-bp MCK 5'-enhancer, but the MCK-SIE is flanked by regions that can repress its activity via the individual and combined effects of about 15 different but highly conserved 9- to 24-bp sequences. ChIP and ChIP-Seq analyses indicate that the SIE and the MCK 5'-enhancer are occupied by MyoD, myogenin and MEF2. Many other E-boxes located within or immediately adjacent to intron 1 are not occupied by MyoD or myogenin. Transgenic analysis of a 6.5-kb MCK genomic fragment containing the 5'-enhancer and proximal promoter plus the 3.2-kb intron 1, with and without MR1, indicates that MR1 is critical for MCK expression in slow- and intermediate-twitch muscle fibers (types I and IIa, respectively), but is not required for expression in fast-twitch muscle fibers (types IIb and IId).ConclusionsIn this study, we discovered that MR1 is critical for MCK expression in slow- and intermediate-twitch muscle fibers and that MR1's positive transcriptional activity depends on a paired E-box MEF2 site motif within a SIE. This is the first study to delineate the DNA controls for MCK expression in different skeletal muscle fiber types.

TBX2 blocks myogenesis and promotes proliferation in rhabdomyosarcoma cells

“…Myogenin and MyoD are used as clinical markers for the diagnosis of RMS, but the MRFs do not function and ectopic expression of the MRFs cannot rescue the activity. 39 Thus, our data suggest that the presence of TBX2 in RMS cells may serve to block the activity of the MRFs. In the human CDKN1A promoter, consensus E-boxes flank the TBX2 consensus-binding motif.…”

“…However, in RMS cells, the aberrant expression of TBX2 may at least partially account for the inactivity of the MRFs observed in RMS cells. Myogenin and MyoD are used as clinical markers for the diagnosis of RMS, but the MRFs do not function and ectopic expression of the MRFs cannot rescue the activity . Thus, our data suggest that the presence of TBX2 in RMS cells may serve to block the activity of the MRFs.…”

Epigenetic landscape during osteoblastogenesis defines a differentiation-dependent Runx2 promoter region

“…In mammals, Mck is controlled by three conserved and experimentally proven regulatory regions: an upstream 206-bp enhancer (−1256 to −1050), a 366-bp proximal promoter (−358 to +7), and a 995-bp intronic enhancer (+904 to +998) (Tai et al, 2011) (Fig. 3).…”

Myogenin Recruits the Histone Chaperone Facilitates Chromatin Transcription (FACT) to Promote Nucleosome Disassembly at Muscle-specific Genes

“…However, it is clear from our data that the presence of both MyoD and myogenin leads to the highest activation in the presence of FACT. MyoD is a more robust transactivator than myogenin and has been shown to be bound to many of the promoters occupied by myogenin (39,40,49,50). Thus, it has been difficult to understand the unique role of myogenin at these genes.…”