CCG-1423-derived compounds reduce global RNA synthesis and inhibit transcriptional responses (ChIP-seq)
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ABSTRACT: Myocardin-related transcription factors (MRTFs) are coactivators of serum response factor (SRF), and thereby regulate cytoskeletal gene expression in response to actin dynamics. MRTFs have also been implicated in heat shock protein (hsp) transcription in fly ovaries, but the mechanisms remain unclear. Here we demonstrate that in mammalian cells, MRTFs are dispensable for hsp gene induction. However, the widely used small molecule inhibitors of MRTF/SRF transcription pathway, derived from CCG-1423, efficiently inhibit hsp gene transcription in both fly and mammalian cells also in absence of MRTFs. Quantifying RNA synthesis and RNA polymerase distribution demonstrates that CCG-1423-derived compounds have a genome-wide effect on transcription. Indeed, tracking nascent transcription at nucleotide resolution reveals that CCG-1423-derived compounds reduce RNA polymerase II elongation, and severely dampen the transcriptional response to heat shock. The effects of CCG-1423-derived compounds therefore extend beyond the MRTF/SRF pathway into nascent transcription, opening novel opportunities for their use in transcription research.
Project description:Myocardin-related transcription factors (MRTFs) are coactivators of serum response factor (SRF), and thereby regulate cytoskeletal gene expression in response to actin dynamics. MRTFs have also been implicated in heat shock protein (hsp) transcription in fly ovaries, but the mechanisms remain unclear. Here we demonstrate that in mammalian cells, MRTFs are dispensable for hsp gene induction. However, the widely used small molecule inhibitors of MRTF/SRF transcription pathway, derived from CCG-1423, efficiently inhibit hsp gene transcription in both fly and mammalian cells also in absence of MRTFs. Quantifying RNA synthesis and RNA polymerase distribution demonstrates that CCG-1423-derived compounds have a genome-wide effect on transcription. Indeed, tracking nascent transcription at nucleotide resolution reveals that CCG-1423-derived compounds reduce RNA polymerase II elongation, and severely dampen the transcriptional response to heat shock. The effects of CCG-1423-derived compounds therefore extend beyond the MRTF/SRF pathway into nascent transcription, opening novel opportunities for their use in transcription research.
Project description:To control transcription, SRF recruits signal-regulated co-activators, the Ternary Complex Factors (TCFs) and the Myocardin-related Transcription Factors (MRTFs), which compete for a common site on its DNA-binding domain. The TCFs - SAP-1, Elk-1 and Net - are Ets proteins that link SRF activity to Ras-ERK signalling. In contrast, the two MRTFs, MRTF-A and MRTF-B, link SRF activity to Rho-actin signalling. In this novel signalling pathway, the actin-binding MRTF RPEL domain acts as a G-actin sensor, controlling MRTF nuclear accumulation in response to signal-induced depletion of the G-actin pool. Previous studies have suggested that the Ras-ERK signalling and Rho-actin pathways control specific subsets of SRF target genes. We used ChIP-seq and RNA-seq to analyse the immediate-early transcriptional response in NIH3T3 fibroblasts, using pathway-specific inhibitors to identify the contributions of Ras-ERK and Rho-actin signalling Chromatin immunoprecipitation and sequencing (ChIP-seq) in NIH3T3 fibroblast after serum stimulation in presence or absence of LatrunculinB or U0126 drugs and using antibodies against SRF, MRTF-A, MRTF-B, SAP1, ELK1, NET, Pol II, PolII S5P, PolII S2P and total H3. Validation by ChIP-PCR. Strand specific total-RNA-seq following DSN normalisation and validation by qRT-PCR from NIH3T3 stimulated by serum or Cytochalasin D in presence or absence of LatrunculinB and/or U0126 drugs.
Project description:Myocardin-related transcription factors (MRTFs) play a central role in the regulation of actin expression and cytoskeletal dynamics. Stimuli that promote actin polymerization allow for shuttling of MRTFs to the nucleus where they activate serum response factor (SRF), a regulator of actin and other cytoskeletal protein genes. SRF is an essential regulator of skeletal muscle differentiation and numerous components of the muscle sarcomere, but the potential involvement of MRTFs in skeletal muscle development has not been examined. We explored the role of MRTFs in muscle development in vivo by generating mutant mice harboring a skeletal muscle-specific deletion of MRTF-B and a global deletion of MRTF-A. These double knockout (dKO) mice were able to form sarcomeres during embryogenesis. However, the sarcomeres were abnormally small and disorganized, causing skeletal muscle hypoplasia and perinatal lethality. Transcriptome analysis demonstrated dramatic dysregulation of actin genes in MRTF dKO mice, highlighting the importance of MRTFs in actin cycling and myofibrillogenesis. MRTFs were also necessary for the survival of skeletal myoblasts and for the efficient formation of intact myotubes. Our findings reveal a central role for MRTFs in sarcomere formation during skeletal muscle development and point to the potential involvement of these transcriptional coactivators in skeletal myopathies. Gene expression profile was generated comparing wild type (WT) and HSA-Cre, MRTF-A/B double knockout mice, by deep seqencing, with three biological replicates, using Illumina HiSeq 2500.
Project description:To control transcription, SRF recruits signal-regulated co-activators, the Ternary Complex Factors (TCFs) and the Myocardin-related Transcription Factors (MRTFs), which compete for a common site on its DNA-binding domain. The TCFs - SAP-1, Elk-1 and Net - are Ets proteins that link SRF activity to Ras-ERK signalling. In contrast, the two MRTFs, MRTF-A and MRTF-B, link SRF activity to Rho-actin signalling. In this novel signalling pathway, the actin-binding MRTF RPEL domain acts as a G-actin sensor, controlling MRTF nuclear accumulation in response to signal-induced depletion of the G-actin pool. Previous studies have suggested that the Ras-ERK signalling and Rho-actin pathways control specific subsets of SRF target genes. We used ChIP-seq and RNA-seq to analyse the immediate-early transcriptional response in NIH3T3 fibroblasts, using pathway-specific inhibitors to identify the contributions of Ras-ERK and Rho-actin signalling
Project description:Myocardin-Related Transcription Factors A and B (MRTF-A and MRTF-B) are highly homologous proteins that function as powerful coactivators of serum response factor (SRF), a ubiquitously expressed transcription factor essential for cardiac development. The SRF/MRTF complex binds to CArG boxes found in the control regions of genes that regulate cytoskeletal dynamics and muscle contraction, among other processes. While SRF is required for heart development and function, the role of MRTFs in the developing or adult heart has not been explored. Through cardiac-specific deletion of MRTF alleles in mice, we show that either MRTF-A or MRTF-B is dispensable for cardiac development and function, whereas deletion of both MRTF-A and MRTF-B causes a spectrum of structural and functional cardiac abnormalities. Defects observed in MRTF-A/B null mice ranged from reduced cardiac contractility and adult onset heart failure to neonatal lethality accompanied by sarcomere disarray. RNA-seq analysis on neonatal hearts identified the most altered pathways in MRTF double knockout hearts as being involved in cytoskeletal organization. Together, these findings demonstrate redundant but essential roles of the MRTFs in maintenance of cardiac structure and function and as indispensible links in cardiac cytoskeletal gene regulatory networks.
Project description:About one third of dilated cardiomyopathy (DCM) cases are caused by mutations in sarcomere or cytoskeletal proteins. Yet treating the cytoskeleton directly is not possible because drugs that bind to actin are not well tolerated. Mutations in the actin binding protein CAP2 can cause DCM and knockout mice, either whole body (CAP2 KO) or cardiomyocyte specific knockouts (CAP2 CKO), develop DCM with cardiac conduction disease. RNA-seq analysis of CAP2 KO hearts and isolated cardiomyocytes revealed over-activation of fetal genes including serum response factor (SRF) regulated genes such as Myl9 and Acta2 prior to the emergence of cardiac disease. To test if we could treat CAP2 KO mice, we synthesized and tested the SRF inhibitor CCG-1423-8u. CCG-1423-8u reduced expression of the SRF targets Myl9 and Acta2, as well as the biomarker of heart failure, NPPA. The median survival of CAP2 CKO mice was 98 days, while CCG-1423-8u treated CKO mice survived for 116 days and also maintain normal cardiac function longer. These results suggest that some forms of sudden cardiac death and cardiac conduction disease are under cytoskeletal stress and that inhibiting signaling through SRF may benefit DCM by reducing cytoskeletal stress.
Project description:Myocardin-related transcription factors (MRTFs) play a central role in the regulation of actin expression and cytoskeletal dynamics. Stimuli that promote actin polymerization allow for shuttling of MRTFs to the nucleus where they activate serum response factor (SRF), a regulator of actin and other cytoskeletal protein genes. SRF is an essential regulator of skeletal muscle differentiation and numerous components of the muscle sarcomere, but the potential involvement of MRTFs in skeletal muscle development has not been examined. We explored the role of MRTFs in muscle development in vivo by generating mutant mice harboring a skeletal muscle-specific deletion of MRTF-B and a global deletion of MRTF-A. These double knockout (dKO) mice were able to form sarcomeres during embryogenesis. However, the sarcomeres were abnormally small and disorganized, causing skeletal muscle hypoplasia and perinatal lethality. Transcriptome analysis demonstrated dramatic dysregulation of actin genes in MRTF dKO mice, highlighting the importance of MRTFs in actin cycling and myofibrillogenesis. MRTFs were also necessary for the survival of skeletal myoblasts and for the efficient formation of intact myotubes. Our findings reveal a central role for MRTFs in sarcomere formation during skeletal muscle development and point to the potential involvement of these transcriptional coactivators in skeletal myopathies.
Project description:The transcription factor SRF is a master regulator of growth factor inducible and cytoskeletal gene expression. Two transcription cofactor families, the TCFs & the MRTFs, are responsible for SRF's activity to direct transcriptional programme in response to extracellular signalling through the Ras-ERK and Rho-actin pathways respectively. We are investigating the role of the SRF network in the response to infection, using the Listeria monocytogenes model. We find that inactivation of the network impairs the ability of CD8 T cells to proliferate in response to listeria and to generate memory cells. Surprisingly, the defect reflects impaired MRTF-SRF signalling rather than the TCF-SRF signalling pathway usually associated with proliferation. Moreover, the defec doesn'tt lie downstream of the initial activation of the TCR, appearing instead to arise from an inability of CD8 T cells to present IL-2 to each other in paracrine fashion. Consistent with these observations, we find that while cultured CD8 MRTF-null T cells can be effectively activated by TCR crosslinking invitro, their ability to form clusters, which is IL-2-dependent, is impaired. Moreover, as expected, pilot experiments indicate that these cells exhibit deficits both in the basal levels of MRTF-SRF target gene expression, and in their ability to induce these genes in response to IL-2 stimulation:
Project description:Chemokine signaling is important for the seeding of different sites by hematopoietic stem cells during development. Serum Response Factor (SRF) controls multiple genes governing adhesion and migration, mainly by recruiting members of the Myocardin-Related Transcription Factor (MRTF) family of G-actin regulated cofactors. We used vav-iCre to inactivate MRTF-SRF signaling early during hematopoietic development. In both Srf- and Mrtf-deleted animals, hematopoiesis in fetal liver and spleen is intact, but does not become established in fetal bone marrow. Srf-null HSC/Ps (hematopoietic stem/progenitor cells) fail to effectively engraft in transplantation experiments, exhibiting normal proximal signaling responses to SDF-1, but reduced adhesiveness, F-actin assembly, and reduced motility. Srf-null HSC/Ps fail to polarise in response to SDF-1, and cannot migrate through restrictive membrane pores to SDF-1 or Scf in vitro. Mrtf-null HSC/Ps were also defective in chemotactic responses to SDF-1. MRTF-SRF signaling is thus critical for the response to chemokine signaling during hematopoietic development. Strand specific RNA sequencing (RNA-seq) in sorted WT and SRF deleted LSK cells with or without a 30 minute SDF stimulation and validation by qRT-PCR