Structure and myofiber-specific expression of the rat muscle regulatory gene MRF4.
We have cloned an 11.3-kb rat genomic DNA fragment encompassing the muscle regulatory factor 4 (MRF4) protein-coding sequence, 8.5 kb of 5'-flanking sequence, and 1.0 kb of 3'-flanking sequence. In order to study MRF4 gene expression, the rat myogenic cell line, L6J1-C, which expresses the endogenous MRF4 gene only in differentiated myofibers, was transfected stably with the full-length genomic clone and various 5' deletions. RNase protection assays demonstrated that MRF4 genes containing as little as 430 bp of 5'-flanking sequence exhibited an increase in expression as the cells differentiated into myofibers, indicating that elements responsible for fiber-specific expression are contained within this cloned DNA fragment. Similar up-regulation was observed with genes containing 1.5 kb of 5'-flanking sequence. Interestingly, MRF4 genes containing 5.0 kb and 8.5 kb of 5'-flanking sequence were up-regulated to even higher levels, suggesting that additional myofiber-specific regulatory elements located between 1.5 and 5.0 kb upstream from the coding region play a role in regulating the expression of this muscle-specific gene.
Hinterberger
T J
TJ
Department of Biological Sciences, Purdue University, West Lafayette, IN 47907.
Mays
J L
JL
Konieczny
S F
SF
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D002460:Cell Line; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics*; D005786:Gene Expression Regulation / Q000235:genetics; D005809:Genes, Regulator; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000737:chemistry / Q000235:genetics*; D009132:Muscles / Q000166:cytology / Q000378:metabolism*; D018006:Myogenic Regulatory Factors; D051381:Rats; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D015183:Restriction Mapping; D014158:Transcription, Genetic / Q000235:genetics
D004268:DNA-Binding Proteins; D009124:Muscle Proteins; D018006:Myogenic Regulatory Factors; C063403:myogenic factor 6