The human c-fos serum response factor and the yeast factors GRM/PRTF have related DNA-binding specificities.

ABSTRACT Primary transcripts encoding the MADS box superfamily of proteins, such as MEF2 in animals and ZEMa in plants, are alternatively spliced, producing several isoformic species. We show here that murine serum response factor (SRF) primary RNA transcripts are alternatively spliced at the fifth exon, deleting approximately one-third of the C-terminal activation domain. Among the different muscle types examined, visceral smooth muscles have a very low ratio of SRFΔ5 to SRF. Increased levels of SRFΔ5 correlates well with reduced smooth muscle contractile gene activity within the elastic aortic arch, suggesting important biological roles for differential expression of SRFΔ5 variant relative to wild-type SRF. SRFΔ5 forms DNA binding-competent homodimers and heterodimers. SRFΔ5 acts as a naturally occurring dominant negative regulatory mutant that blocks SRF-dependent skeletal α-actin, cardiac α-actin, smooth α-actin, SM22α, and SRF promoter-luciferase reporter activities. Expression of SRFΔ5 interferes with differentiation of myogenic C2C12 cells and the appearance of skeletal α-actin and myogenin mRNAs. SRFΔ5 repressed the serum-induced activity of the c-fos serum response element. SRFΔ5 fused to the yeast Gal4 DNA binding domain displayed low transcriptional activity, which was complemented by overexpression of the coactivator ATF6. These results indicate that the absence of exon 5 might be bypassed through recruitment of transcription factors that interact with extra-exon 5 regions in the transcriptional activating domain. The novel alternatively spliced isoform of SRF, SRFΔ5, may play an important regulatory role in modulating SRF-dependent gene expression.

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Recruitment of the tinman homolog Nkx-2.5 by serum response factor activates cardiac alpha-actin gene transcription.

Molecular and Cellular Biology ◽

10.1128/mcb.16.11.6372 ◽

1996 ◽

Vol 16 (11) ◽

pp. 6372-6384 ◽

Cited By ~ 219

Author(s):

C Y Chen ◽

R J Schwartz

Keyword(s):

Dna Binding ◽

Serum Response Factor ◽

Binding Activity ◽

Dominant Negative ◽

Actin Gene ◽

Response Factor ◽

Dna Binding Activity ◽

Actin Promoter ◽

Alpha Actin ◽

Serum Response

We recently showed that the cardiogenic homeodomain factor Nkx-2.5 served as a positive acting accessory factor for serum response factor (SRF) and that together they provided strong transcriptional activation of the cardiac alpha-actin promoter, depending upon intact serum response elements (SREs) (C. Y. Chen, J. Croissant, M. Majesky, S. Topouz, T. McQuinn, M. J. Frankovsky, and R. J. Schwartz, Dev. Genet. 19:119-130, 1996). As shown here, Nkx-2.5 and SRF collaborated to activate the endogenous murine cardiac alpha-actin gene in 10T1/2 fibroblasts by a mechanism in which SRF recruited Nkx-2.5 to the alpha-actin promoter. Activation of a truncated promoter consisting of the proximal alpha-actin SRE1 occurred even when Nkx-2.5 DNA-binding activity was blocked by a point mutation in the third helix of its homeodomain. Investigation of protein-protein interactions showed that Nkx-2.5 was bound to SRF in the absence of DNA in soluble protein complexes retrieved from cardiac myocyte nuclei but could also be detected in coassociated binding complexes on the proximal SRE1. Recruitment of Nkx-2.5 to an SRE depended upon SRF DNA-binding activity and was blocked by the dominant negative SRFpm1 mutant, which allowed for dimerization of SRF monomers but prevented DNA binding. Interactive regions shared by Nkx-2.5 and SRF were mapped to N-terminal/helix I and helix II/helix III regions of the Nkx-2.5 homeodomain and to the N-terminal extension of the MADS box. Our study suggests that physical association between Nkx-2.5 and SRF is one way that cardiac specified genes are activated in cardiac cell lineages.

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Enhancement of Serum-response Factor-dependent Transcription and DNA Binding by the Architectural Transcription Factor HMG-I(Y)

Journal of Biological Chemistry ◽

10.1074/jbc.273.16.9755 ◽

1998 ◽

Vol 273 (16) ◽

pp. 9755-9760 ◽

Cited By ~ 52

Author(s):

Michael T. Chin ◽

Andrea Pellacani ◽

Hong Wang ◽

Sharon S. J. Lin ◽

Mukesh K. Jain ◽

...

Keyword(s):

Transcription Factor ◽

Dna Binding ◽

Serum Response Factor ◽

Response Factor ◽

Serum Response

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Regulatory role of MEF2D in serum induction of the c-jun promoter.

Molecular and Cellular Biology ◽

10.1128/mcb.15.6.2907 ◽

1995 ◽

Vol 15 (6) ◽

pp. 2907-2915 ◽

Cited By ~ 129

Author(s):

T H Han ◽

R Prywes

Keyword(s):

Dna Binding ◽

Reporter Gene ◽

Hela Cells ◽

Serum Response Factor ◽

Common Mechanism ◽

Response Factor ◽

3T3 Cells ◽

Nih 3T3 ◽

Serum Response ◽

Nih 3T3 Cells

Serum induction of c-jun expression in HeLa cells requires a MEF2 site at -59 in the c-jun promoter. MEF2 sites, found in many muscle-specific enhancers, are bound by a family of transcription factors, MEF2A through -D, which are related to serum response factor in their DNA binding domains. We have found that MEF2D is the predominant protein in HeLa cells that binds to the c-jun MEF2 site. Serum induction of a MEF2 reporter gene was not observed in a line of NIH 3T3 cells which contain low MEF2 site binding activity. Transfection of MEF2D into NIH 3T3 cells reconstituted serum induction, demonstrating that MEF2D is required for the serum response. Deletion analysis of MEF2D showed that its DNA binding domain, when fused to a heterologous transcriptional activation domain, was sufficient for serum induction of a MEF2 reporter gene. This is the domain homologous to that in the serum response factor which is required for serum induction of the c-fos serum response element, suggesting that serum regulation of c-fos and c-jun may share a common mechanism.

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Human and Drosophila Homeodomain Proteins That Enhance the DNA-Binding Activity of Serum Response Factor

Science ◽

10.1126/science.257.5073.1089 ◽

1992 ◽

Vol 257 (5073) ◽

pp. 1089-1095 ◽

Cited By ~ 173

Author(s):

D. A. Grueneberg ◽

S. Natesan ◽

C. Alexandre ◽

M. Z. Gilman

Keyword(s):

Dna Binding ◽

Serum Response Factor ◽

Binding Activity ◽

Response Factor ◽

Homeodomain Proteins ◽

Dna Binding Activity ◽

Serum Response

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Identification of transcriptional activation and inhibitory domains in serum response factor (SRF) by using GAL4-SRF constructs

Molecular and Cellular Biology ◽

10.1128/mcb.13.8.4640-4647.1993 ◽

1993 ◽

Vol 13 (8) ◽

pp. 4640-4647

Author(s):

F E Johansen ◽

R Prywes

Keyword(s):

Amino Acids ◽

Dna Binding ◽

Transcriptional Activation ◽

Serum Response Factor ◽

Binding Domain ◽

Response Factor ◽

Dna Binding Domain ◽

Activation Domain ◽

Transcriptional Activation Domain ◽

Serum Response

The binding of serum response factor (SRF) to the c-fos serum response element has been shown to be essential for serum and growth factor activation of c-Fos. Since SRF is ubiquitously expressed, it has been difficult to measure the activity of SRF introduced into cells. To assay for functions of SRF in cells, we have changed its DNA binding specificity by fusing it to the DNA binding domain of GAL4. Transfection of GAL4-SRF constructs into cells has allowed us to identify SRF's transcriptional activation domain as well as domains which inhibit this activity. First, we found that the transcriptional activation domain maps to between amino acids 339 and 508 in HeLa cells and to between amino acids 414 and 508 in NIH 3T3 cells. Second, we show that in the context of GAL4-SRF constructs, there are two separate domains of SRF that can inhibit its activation domain. Although these domains overlap the DNA binding and dimerization domains of SRF, these functions were not required for inhibition. Finally, we show that one of the inhibitory domains is modular in that it can also inhibit activation when it is moved amino terminal to GAL4's DNA binding domain in an SRF-GAL4-SRF construct. The implications of these inhibitory domains for SRF regulation are discussed.

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Proliferin, a Prolactin/Growth Hormone-Like Peptide Represses Myogenic-Specific Transcription by the Suppression of an Essential Serum Response Factor-Like DNA-Binding Activity

Molecular Endocrinology ◽

10.1210/mend-5-6-802 ◽

1991 ◽

Vol 5 (6) ◽

pp. 802-814 ◽

Cited By ~ 13

Author(s):

George E. O. Muscat ◽

Kari Gobius ◽

Jacqueline Emery

Keyword(s):

Growth Hormone ◽

Dna Binding ◽

Serum Response Factor ◽

Binding Activity ◽

Response Factor ◽

Dna Binding Activity ◽

Serum Response

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MAL and Ternary Complex Factor Use Different Mechanisms To Contact a Common Surface on the Serum Response Factor DNA-Binding Domain

Molecular and Cellular Biology ◽

10.1128/mcb.01902-05 ◽

2006 ◽

Vol 26 (11) ◽

pp. 4134-4148 ◽

Cited By ~ 61

Author(s):

Alexia-Ileana Zaromytidou ◽

Francesc Miralles ◽

Richard Treisman

Keyword(s):

Dna Binding ◽

Complex Formation ◽

Ternary Complex ◽

Serum Response Factor ◽

Dna Bending ◽

Binding Domain ◽

Response Factor ◽

Dna Binding Domain ◽

Serum Response ◽

Ternary Complex Factor

ABSTRACT The transcription factor serum response factor (SRF) interacts with its cofactor, MAL/MKL1, a member of the myocardin-related transcription factor (MRTF) family, through its DNA-binding domain. We define a seven-residue sequence within the conserved MAL B1 region essential and sufficient for complex formation. The neighboring Q-box sequence facilitates this interaction. The B1 and Q-box regions also have antagonistic effects on MAL nuclear import, but the residues involved are largely distinct. Both MAL and the ternary complex factor (TCF) family of SRF cofactors interact with a hydrophobic groove and pocket on the SRF DNA-binding domain. Unlike the TCFs, however, interaction of MAL with SRF is impaired by SRF αI-helix mutations that reduce DNA bending in the SRF-DNA complex. A clustered SRF αI-helix mutation strongly impairs MAL-SRF complex formation but does not affect DNA distortion in the MAL-SRF complex. MAL-SRF complex formation is facilitated by DNA binding. DNase I footprinting indicates that in the SRF-MAL complex MAL directly contacts DNA. These contacts, which flank the DNA sequences protected from DNase I by SRF, are required for effective MAL-SRF complex formation in gel mobility shift assays. We propose a model of MAL-SRF complex formation in which MAL interacts with SRF by the addition of a β-strand to the SRF DNA-binding domain β-sheet region, while SRF-induced DNA bending facilitates MAL-DNA contact.

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Persistent Increased DNA-Binding and Expression of Serum Response Factor Occur with Epilepsy-Associated Long-Term Plasticity Changes

Journal of Neuroscience ◽

10.1523/jneurosci.19-19-08234.1999 ◽

1999 ◽

Vol 19 (19) ◽

pp. 8234-8243 ◽

Cited By ~ 28

Author(s):

T. Allen Morris ◽

Neda Jafari ◽

Ann C. Rice ◽

Olavo Vasconcelos ◽

Robert J. DeLorenzo

Keyword(s):

Dna Binding ◽

Serum Response Factor ◽

Response Factor ◽

Serum Response

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MCM1 point mutants deficient in expression of alpha-specific genes: residues important for interaction with alpha 1.

Molecular and Cellular Biology ◽

10.1128/mcb.14.4.2534 ◽

1994 ◽

Vol 14 (4) ◽

pp. 2534-2544 ◽

Cited By ~ 37

Author(s):

L Bruhn ◽

G F Sprague

Keyword(s):

Dna Binding ◽

Serum Response Factor ◽

Specific Gene ◽

Response Factor ◽

Binding Assays ◽

Yeast Saccharomyces Cerevisiae ◽

Coregulatory Proteins ◽

Serum Response

Complexes formed between MCM1 and several coregulatory proteins--alpha 1, alpha 2, and STE12--serve to govern transcription of the a- and alpha-specific gene sets in the yeast Saccharomyces cerevisiae. The N-terminal third of MCM1, MCM1(1-98), which includes a segment homologous to mammalian serum response factor, is capable of performing all of the functions necessary for cell-type-specific gene regulation, including DNA binding and interaction with coregulatory proteins. To explore the mechanisms by which MCM1(1-98) functions, we isolated point mutants that are specifically deficient in alpha-specific gene expression in vivo, anticipating that many of the mutants would be impaired for interaction with alpha 1. Indeed, in vitro DNA binding assays revealed that a substantial number of the mutants were specifically defective in the ability to bind cooperatively with alpha 1. Two other mutant classes were also found. One class, exemplified most clearly by substitutions at residues 22 and 27, exhibited a general defect in DNA binding. The second class, exemplified by substitutions at residues 33 and 41, was proficient at DNA binding and interaction with alpha 1 in vitro, suggesting that these mutants may be defective in achieving an alpha 1-mediated conformational change required for transcription activation in vivo. Most of the mutants defective for interaction with alpha 1 had substitutions within residues 69 to 81, which correspond to a region of serum response factor important for interaction with its coregulatory proteins. A subset of the mutants with changes in this region were also defective in the ability to bind with STE12 to DNA from an a-specific gene, suggesting that a common region of MCM1(1-98) mediates interaction with both alpha 1 and STE12. This region of MCM1 does not seem to constitute an independent domain of the protein, however, because some substitutions within this region affected DNA binding. Only two of the MCM1(1-98) point mutants showed significant defects in the ability to form complexes with alpha 2, suggesting that the mechanism by which MCM1 interacts with alpha 2 is distinct from that by which it interacts with alpha 1 and STE12.

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