Sequence-specific recruitment of transcriptional co-repressor Cabin1 by myocyte enhancer factor-2.
ABSTRACT The myocyte enhancer factor-2 (MEF2) family of transcription factors has important roles in the development and function of T cells, neuronal cells and muscle cells. MEF2 is capable of repressing or activating transcription by association with a variety of co-repressors or co-activators in a calcium-dependent manner. Transcriptional repression by MEF2 has attracted particular attention because of its potential role in hypertrophic responses of cardiomyocytes. Several MEF2 co-repressors, such as Cabin1/Cain and class II histone deacetylases (HDACs), have been identified. However, the molecular mechanism of their recruitment to specific promoters by MEF2 remains largely unknown. Here we report a crystal structure of the MADS-box/MEF2S domain of human MEF2B bound to a motif of the transcriptional co-repressor Cabin1 and DNA at 2.2 A resolution. The crystal structure reveals a stably folded MEF2S domain on the surface of the MADS box. Cabin1 adopts an amphipathic alpha-helix to bind a hydrophobic groove on the MEF2S domain, forming a triple-helical interaction. Our studies of the ternary Cabin1/MEF2/DNA complex show a general mechanism by which MEF2 recruits transcriptional co-repressor Cabin1 and class II HDACs to specific DNA sites.
- SourceAvailable from: Xuemei Han[Show abstract] [Hide abstract]
ABSTRACT: Redox-mediated posttranslational modifications represent a molecular switch that controls major mechanisms of cell function. Nitric oxide (NO) can mediate redox reactions via S-nitrosylation, representing transfer of an NO group to a critical protein thiol. NO is known to modulate neurogenesis and neuronal survival in various brain regions in disparate neurodegenerative conditions. However, a unifying molecular mechanism linking these phenomena remains unknown. Here, we report that S-nitrosylation of myocyte enhancer factor 2 (MEF2) transcription factors acts as a redox switch to inhibit both neurogenesis and neuronal survival. Structure-based analysis reveals that MEF2 dimerization creates a pocket, facilitating S-nitrosylation at an evolutionally conserved cysteine residue in the DNA binding domain. S-Nitrosylation disrupts MEF2-DNA binding and transcriptional activity, leading to impaired neurogenesis and survival in vitro and in vivo. Our data define a molecular switch whereby redox-mediated posttranslational modification controls both neurogenesis and neurodegeneration via a single transcriptional signaling cascade.Cell reports. 07/2014;
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ABSTRACT: Using reverse transcriptase- polymerase chain reaction (RT-PCR), the cDNA encoding a new isoform of the myocyte enhancer factor-2 (BMEF2) was cloned from the brain of the strain "Liangguang 2" of Bombyx mori. The open reading frame (ORF) of the new isoform shows 12 nucleotides absence of (GCACTCACAAAG) and three nucleotides mutation to the former BMEF2 (GenBank no. AB121093). Thus, we named it BMEF2B (GenBank no. EF100967). Using the SWISS-MODEL Prediction Server, the 3- D structure of BMEF2B was modeled. There are two �-turns and three �-helixes predicted in BMEF2B, with the pattern of �-�-�-�-�. The BMEF2B mRNA was detected not only in the central nervous system (CNS), including brain, suboesophageal ganglion (SG), thoracic ganglion (TG), and abdominal ganglion (AG), but in the non-neural tissues, such as the midgut (Mg), fat body (FB), and epidermis (Ep), muscle (Ms) and ovary (Ov). BMEF2B mRNA content in the brain was measured using the combined method of quantitative RT-PCR and Southern blotting, which kept consistently high from larvae to adults.01/2010;
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ABSTRACT: MEF2B encodes a transcriptional activator and is mutated in ∼11% of diffuse large B cell lymphomas (DLBCLs) and ∼12% of follicular lymphomas (FLs). Here we found that MEF2B directly activated the transcription of the proto-oncogene BCL6 in normal germinal-center (GC) B cells and was required for DLBCL proliferation. Mutation of MEF2B resulted in enhanced transcriptional activity of MEF2B either through disruption of its interaction with the corepressor CABIN1 or by rendering it insensitive to inhibitory signaling events mediated by phosphorylation and sumoylation. Consequently, the transcriptional activity of Bcl-6 was deregulated in DLBCLs with MEF2B mutations. Thus, somatic mutations of MEF2B may contribute to lymphomagenesis by deregulating BCL6 expression, and MEF2B may represent an alternative target for blocking Bcl-6 activity in DLBCLs.Nature Immunology 08/2013; · 24.97 Impact Factor