The Mouse MRF4 Promoter Is trans-Activated Directly and Indirectly by Muscle-specific Transcription Factors

doi:10.1074/jbc.270.7.2889

The Mouse MRF4 Promoter Is trans-Activated Directly and Indirectly by Muscle-specific Transcription Factors (*)

From the Department of Biochemistry and Molecular Biology, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030

** To whom correspondence should be addressed:
Dept. of Biochemistry and Molecular Biology, Box 117, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030.
Tel.: 713-792-3648; Fax: 713-791-9478.

Abstract

MRF4 is a member of the basic helix-loop-helix (bHLH) family of muscle-specific transcription factors, which also includes MyoD, myogenin, and myf5. The myocyte enhancer binding factor 2 (MEF2) proteins also serve as important muscle-specific transcription factors. In addition to activating the expression of many muscle-specific structural genes, various members of these two classes of proteins activate their own expression and the expression of each other in a complex transcriptional network that results in the establishment and maintenance of the muscle phenotype. To begin to determine how the expression of MRF4 is regulated by other muscle-specific transcription factors, we have isolated a region of the MRF4 gene that confers muscle-specific expression and have analyzed this promoter region for cis-acting elements involved in trans-activation by the myogenic bHLH and MEF2 transcription factors. Here, we show that in 10T1/2 fibroblasts the MRF4 promoter is trans-activated by myogenin, MyoD, myf5, and by the MEF2 factors, but that MRF4 does not activate expression of its own promoter. Myogenin activated the MRF4 promoter directly by an E box-dependent mechanism, while MEF2 factors activated the promoter through an indirect pathway. The E box-dependent regulation of the MRF4 promoter is in contrast to the regulation of the myogenin and MyoD promoters and may represent a mechanism for the differential expression of these factors during myogenesis.

Footnotes

↵^§ American Cancer Society postdoctoral fellow.
↵^¶ Supported by a National Institutes of Health training grant.
↵* This work was supported in part by grants from the National Institutes of Health, the Muscular Dystrophy Association, and the Robert A. Welch Foundation (to E. N. O.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) U18131[GenBank].
↵¹ The abbreviations used are:

bHLH

basic helix-loop-helix

MEF2

myocyte enhancer-binding factor 2

PCR

polymerase chain reaction

CAT

chloramphenicol acetyltransferase

DM

differentiation medium

GM

growth medium

bp

base pair(s).
- Received November 18, 1994.
- Revision received December 13, 1994.