Senescence represses the nuclear localization of the serum response factor and differentiation regulates its nuclear localization with lineage specificity

The differentiation of cultured 3T3T mesenchymal stem cells into adipocytes represses growth factor responsiveness by limiting the nuclear localization of the serum response factor (SRF) that binds to and activates the promoters of growth control genes that contain the serum response elements (SRE), such as junB and c-fos. The regulation of SRF nuclear localization by adipocyte differentiation is specific, because we show that adipocyte differentiation does not repress the nuclear localization of six other transacting factors. To determine if repression of growth factor responsiveness that occurs during senescence also represses the nuclear localization of SRF, we studied normal human WI-38 fibroblasts at low versus high population doublings. The results show that SRF localizes to the nucleus of proliferative cells whereas in senescent cells SRF can not be detected in the nucleus. This result is apparent in both immunofluorescence assays and in western blot analysis. We next evaluated the cellular distribution of SRF in selected human tissues to determine whether the loss of proliferative potential in vivo could have a different effect on SRF nuclear localization. We found that in cells of the small bowel mucosa, differentiation modulates SRF nuclear localization in an opposite manner. Minimal SRF expression and nuclear localization is evident in undifferentiated cells at the base of crypts whereas increased SRF expression and nuclear localization is evident in differentiated cells at the surface tip of the villus. These results together establish that regulation of SRF expression and nuclear localization is important in senescence and differentiation in a lineage specific manner.

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A growth factor-induced kinase phosphorylates the serum response factor at a site that regulates its DNA-binding activity.

Molecular and Cellular Biology ◽

10.1128/mcb.13.10.6260 ◽

1993 ◽

Vol 13 (10) ◽

pp. 6260-6273 ◽

Cited By ~ 176

Author(s):

V M Rivera ◽

C K Miranti ◽

R P Misra ◽

D D Ginty ◽

R H Chen ◽

...

Keyword(s):

Growth Factor ◽

Serum Response Factor ◽

Critical Role ◽

Response Factor ◽

Serum Response Element ◽

Response Element ◽

Ribosomal S6 Kinase ◽

Serum Response

A signaling pathway by which growth factors may induce transcription of the c-fos proto-oncogene has been characterized. Growth factor stimulation of quiescent fibroblasts activates a protein kinase cascade that leads to the rapid and transient phosphorylation of the serum response factor (SRF), a regulator of c-fos transcription. The in vivo kinetics of SRF phosphorylation and dephosphorylation parallel the activation and subsequent repression of c-fos transcription, suggesting that this phosphorylation event plays a critical role in the control of c-fos expression. The ribosomal S6 kinase pp90rsk, a growth factor-inducible kinase, phosphorylates SRF in vitro at serine 103, the site that becomes newly phosphorylated upon growth factor stimulation in vivo. Phosphorylation of serine 103 significantly enhances the affinity and rate with which SRF associates with its binding site, the serum response element, within the c-fos promoter. These results suggest a model in which the growth factor-induced phosphorylation of SRF at serine 103 contributes to the activation of c-fos transcription by facilitating the formation of an active transcription complex at the serum response element.

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A growth factor-induced kinase phosphorylates the serum response factor at a site that regulates its DNA-binding activity

Molecular and Cellular Biology ◽

10.1128/mcb.13.10.6260-6273.1993 ◽

1993 ◽

Vol 13 (10) ◽

pp. 6260-6273

Author(s):

V M Rivera ◽

C K Miranti ◽

R P Misra ◽

D D Ginty ◽

R H Chen ◽

...

Keyword(s):

Growth Factor ◽

Serum Response Factor ◽

Critical Role ◽

Response Factor ◽

Serum Response Element ◽

Response Element ◽

Ribosomal S6 Kinase ◽

Serum Response

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Myozap, a Novel Intercalated Disc Protein, Activates Serum Response Factor–Dependent Signaling and Is Required to Maintain Cardiac Function In Vivo

Circulation Research ◽

10.1161/circresaha.109.213256 ◽

2010 ◽

Vol 106 (5) ◽

pp. 880-890 ◽

Cited By ~ 37

Author(s):

Thalia S. Seeger ◽

Derk Frank ◽

Claudia Rohr ◽

Rainer Will ◽

Steffen Just ◽

...

Keyword(s):

Cardiac Function ◽

Serum Response Factor ◽

Response Factor ◽

Intercalated Disc ◽

Serum Response

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Functional antagonism between YY1 and the serum response factor

Molecular and Cellular Biology ◽

10.1128/mcb.12.9.4209-4214.1992 ◽

1992 ◽

Vol 12 (9) ◽

pp. 4209-4214

Author(s):

A Gualberto ◽

D LePage ◽

G Pons ◽

S L Mader ◽

K Park ◽

...

Keyword(s):

Serum Response Factor ◽

Regulatory Element ◽

Target Sequence ◽

Response Factor ◽

Basal Expression ◽

Actin Promoter ◽

Alpha Actin ◽

Serum Response

The rapid, transient induction of the c-fos proto-oncogene by serum growth factors is mediated by the serum response element (SRE). The SRE shares homology with the muscle regulatory element (MRE) of the skeletal alpha-actin promoter. It is not known how these elements respond to proliferative and cell-type-specific signals, but the response appears to involve the binding of the serum response factor (SRF) and other proteins. Here, we report that YY1, a multifunctional transcription factor, binds to SRE and MRE sequences in vitro. The methylation interference footprint of YY1 overlaps with that of the SRF, and YY1 competes with the SRF for binding to these DNA elements. Overexpression of YY1 repressed serum-inducible and basal expression from the c-fos promoter and repressed basal expression from the skeletal alpha-actin promoter. YY1 also repressed expression from the individual SRE and MRE sequences upstream from a TATA element. Unlike that of YY1, SRF overexpression alone did not influence the transcriptional activity of the target sequence, but SRF overexpression could reverse YY1-mediated trans repression. These data suggest that YY1 and the SRF have antagonistic functions in vivo.

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Cardiomyopathy in transgenic mice with cardiac-specific overexpression of serum response factor

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.2001.280.4.h1782 ◽

2001 ◽

Vol 280 (4) ◽

pp. H1782-H1792 ◽

Cited By ~ 92

Author(s):

Xiaomin Zhang ◽

Gohar Azhar ◽

Jianyuan Chai ◽

Pamela Sheridan ◽

Koichiro Nagano ◽

...

Keyword(s):

Transgenic Mice ◽

Cardiac Muscle ◽

Serum Response Factor ◽

Interstitial Fibrosis ◽

Weight Ratio ◽

Heart Weight ◽

Cardiomyocyte Hypertrophy ◽

Response Factor ◽

Serum Response

Serum response factor (SRF), a member of the MCM1, agamous, deficiens, SRF (MADS) family of transcriptional activators, has been implicated in the transcriptional control of a number of cardiac muscle genes, including cardiac α-actin, skeletal α-actin, α-myosin heavy chain (α-MHC), and β-MHC. To better understand the in vivo role of SRF in regulating genes responsible for maintenance of cardiac function, we sought to test the hypothesis that increased cardiac-specific SRF expression might be associated with altered cardiac morphology and function. We generated transgenic mice with cardiac-specific overexpression of the human SRF gene. The transgenic mice developed cardiomyopathy and exhibited increased heart weight-to-body weight ratio, increased heart weight, and four-chamber dilation. Histological examination revealed cardiomyocyte hypertrophy, collagen deposition, and interstitial fibrosis. SRF overexpression altered the expression of SRF-regulated genes and resulted in cardiac muscle dysfunction. Our results demonstrate that sustained overexpression of SRF, in the absence of other stimuli, is sufficient to induce cardiac change and suggest that SRF is likely to be one of the downstream effectors of the signaling pathways involved in mediating cardiac hypertrophy.

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Nuclear import of serum response factor (SRF) requires a short amino-terminal nuclear localization sequence and is independent of the casein kinase II phosphorylation site

Journal of Cell Science ◽

10.1242/jcs.107.11.3029 ◽

1994 ◽

Vol 107 (11) ◽

pp. 3029-3036

Author(s):

J. Rech ◽

I. Barlat ◽

J.L. Veyrune ◽

A. Vie ◽

J.M. Blanchard

Keyword(s):

Amino Acids ◽

Nuclear Localization ◽

Serum Response Factor ◽

Phosphorylation Site ◽

Casein Kinase Ii ◽

Casein Kinase ◽

Resting Cells ◽

Response Factor ◽

Amino Terminal ◽

Serum Response

Serum stimulation of resting cells is mediated at least in part at the transcriptional level by the activation of numerous genes among which c-fos constitutes a model. Serum response factor (SRF) forms a ternary complex at the c-fos serum response element (SRE) with an accessory protein p62TCF/Elk-1. Both proteins are the targets of multiple phosphorylation events and their role is still unknown in the amino terminus of SRF. While the transcriptional activation domain has been mapped between amino acids 339 and 508, the DNA-binding and the dimerization domains have been mapped to between amino acids 133–235 and 168–235, respectively, no role has been proposed for the amino-terminal portion of the molecule. We demonstrate in the present work that amino acids 95 to 100 contain a stretch of basic amino acids that are sufficient to target a reporter protein to the nucleus. Moreover, this sequence appears to be the only nuclear localization signal operating in SRF. Finally, whereas the global structure around this putative nuclear location signal is reminiscent of what is found in the SV40 T antigen, the casein kinase II phosphorylation site does not determine the rate of cyto-nuclear protein transport of this protein.

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New Role for Serum Response Factor in Postnatal Skeletal Muscle Growth and Regeneration via the Interleukin 4 and Insulin-Like Growth Factor 1 Pathways

Molecular and Cellular Biology ◽

10.1128/mcb.00138-06 ◽

2006 ◽

Vol 26 (17) ◽

pp. 6664-6674 ◽

Cited By ~ 53

Author(s):

Claude Charvet ◽

Christophe Houbron ◽

Ara Parlakian ◽

Julien Giordani ◽

Charlotte Lahoute ◽

...

Keyword(s):

Gene Expression ◽

Skeletal Muscle ◽

Growth Factor ◽

Serum Response Factor ◽

Muscle Growth ◽

Interleukin 4 ◽

Specific Gene ◽

Response Factor ◽

Insulin Like Growth Factor ◽

Serum Response

ABSTRACT Serum response factor (SRF) is a crucial transcriptional factor for muscle-specific gene expression. We investigated SRF function in adult skeletal muscles, using mice with a postmitotic myofiber-targeted disruption of the SRF gene. Mutant mice displayed severe skeletal muscle mass reductions due to a postnatal muscle growth defect resulting in highly hypotrophic adult myofibers. SRF-depleted myofibers also failed to regenerate following injury. Muscles lacking SRF had very low levels of muscle creatine kinase and skeletal alpha-actin (SKA) transcripts and displayed other alterations to the gene expression program, indicating an overall immaturity of mutant muscles. This loss of SKA expression, together with a decrease in beta-tropomyosin expression, contributed to myofiber growth defects, as suggested by the extensive sarcomere disorganization found in mutant muscles. However, we observed a downregulation of interleukin 4 (IL-4) and insulin-like growth factor 1 (IGF-1) expression in mutant myofibers which could also account for their defective growth and regeneration. Indeed, our demonstration of SRF binding to interleukin 4 and IGF-1 promoters in vivo suggests a new crucial role for SRF in pathways involved in muscle growth and regeneration.

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Cardiac Tissue Enriched Factors Serum Response Factor and GATA-4 Are Mutual Coregulators

Molecular and Cellular Biology ◽

10.1128/mcb.20.20.7550-7558.2000 ◽

2000 ◽

Vol 20 (20) ◽

pp. 7550-7558 ◽

Cited By ~ 146

Author(s):

Narasimhaswamy S. Belaguli ◽

Jorge L. Sepulveda ◽

Vishal Nigam ◽

Frédéric Charron ◽

Mona Nemer ◽

...

Keyword(s):

Zinc Finger ◽

Cardiac Tissue ◽

Serum Response Factor ◽

Zinc Finger Protein ◽

Response Factor ◽

Mads Box ◽

Cardiovascular Tissue ◽

Serum Response

ABSTRACT Combinatorial interaction among cardiac tissue-restricted enriched transcription factors may facilitate the expression of cardiac tissue-restricted genes. Here we show that the MADS box factor serum response factor (SRF) cooperates with the zinc finger protein GATA-4 to synergistically activate numerous myogenic and nonmyogenic serum response element (SRE)-dependent promoters in CV1 fibroblasts. In the absence of GATA binding sites, synergistic activation depends on binding of SRF to the proximal CArG box sequence in the cardiac and skeletal α-actin promoter. GATA-4's C-terminal activation domain is obligatory for synergistic coactivation with SRF, and its N-terminal domain and first zinc finger are inhibitory. SRF and GATA-4 physically associate both in vivo and in vitro through their MADS box and the second zinc finger domains as determined by protein A pullout assays and by in vivo one-hybrid transfection assays using Gal4 fusion proteins. Other cardiovascular tissue-restricted GATA factors, such as GATA-5 and GATA-6, were equivalent to GATA-4 in coactivating SRE-dependent targets. Thus, interaction between the MADS box and C4 zinc finger proteins, a novel regulatory paradigm, mediates activation of SRF-dependent gene expression.

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Delayed liver regeneration in mice lacking liver serum response factor

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00493.2006 ◽

2007 ◽

Vol 292 (4) ◽

pp. G996-G1001 ◽

Cited By ~ 7

Author(s):

M. Ujue Latasa ◽

Dominique Couton ◽

Claude Charvet ◽

Aurélie Lafanechère ◽

Jacques-Emmanuel Guidotti ◽

...

Keyword(s):

Liver Regeneration ◽

Partial Hepatectomy ◽

Serum Response Factor ◽

Early Response ◽

Mutant Mice ◽

Response Factor ◽

Impaired Liver ◽

Serum Response

Various immediate early genes (IEGs) upregulated during the early process of liver regeneration are transcriptional targets of the serum response factor (SRF). We show here that the expression of SRF is rapidly induced in rodent liver after partial hepatectomy. Because the inactivation of the SRF gene in mice is embryonic lethal, the in vivo role of SRF in liver regeneration after partial hepatectomy was analyzed in mutant mice conditionally deleted for SRF in the liver. We demonstrate that SRF is not an essential factor for liver ontogenesis. However, adult mutant mice show impaired liver regeneration after partial hepatectomy, associated with a blunted upregulation of various SRF target IEGs. In conclusion, our work suggests that SRF is an early response transcription factor that may contribute to the initial phases of liver regeneration through its activation of IEGs.

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