Myogenic regulatory factors (MRF) are
basic helix-loop-helix (bHLH)
transcription factor
In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The f ...
s that regulate
myogenesis
Myogenesis is the formation of skeletal muscular tissue, particularly during embryonic development.
Muscle fibers generally form through the fusion of precursor myoblasts into multinucleated fibers called ''myotubes''. In the early development o ...
:
MyoD
MyoD, also known as myoblast determination protein 1, is a protein in animals that plays a major role in regulating muscle differentiation. MyoD, which was discovered in the laboratory of Harold M. Weintraub, belongs to a family of proteins kno ...
,
Myf5,
myogenin
Myogenin, is a transcriptional activator encoded by the MYOG gene.
Myogenin is a muscle-specific basic-helix-loop-helix (bHLH) transcription factor involved in the coordination of skeletal muscle development or myogenesis and repair. Myogenin is ...
, and
MRF4.
These proteins contain a conserved basic
DNA binding domain
A DNA-binding domain (DBD) is an independently folded protein domain that contains at least one structural motif that recognizes double- or single-stranded DNA. A DBD can recognize a specific DNA sequence (a recognition sequence) or have a genera ...
that binds the
E box An E-box (enhancer box) is a DNA response element found in some eukaryotes that acts as a protein-binding site and has been found to regulate gene expression in neurons, muscles, and other tissues. Its specific DNA sequence, CANNTG (where N can ...
DNA motif. They dimerize with other
HLH containing proteins through an HLH-HLH interaction.
MRF Gene Family Evolution
There are typically four vertebrate MRF
paralogues
Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a spec ...
which are homologous to typically a single MRF gene in
non-vertebrates. These four genes are thought to have been duplicated in the
two rounds of whole-genome duplication early in
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with ...
evolution that played a role in the evolution of more complex vertebrate body plans. The four MRFs have four distinct
expression profiles, though with some redundancy, as
MyoD
MyoD, also known as myoblast determination protein 1, is a protein in animals that plays a major role in regulating muscle differentiation. MyoD, which was discovered in the laboratory of Harold M. Weintraub, belongs to a family of proteins kno ...
and
Myf5 are both involved in myoblast determination, and are followed by the activation of
Myf6 (MRF4) and
Myog in myoblast differentiation. There have also been instances of independent duplication of the MRFs in invertebrate lineages, similarly followed by
subfunctionalization of the expression of the genes in time and/or in space. In
amphioxus, an invertebrate chordate closely related to vertebrates, there are five MRFs which are expressed in different patterns during development.
References
External links
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{{Transcription factors, g1
Transcription factors
DNA-binding proteins