A conserved 28-base-pair element (HF-1) in the rat cardiac myosin light-chain-2 gene confers cardiac-specific and alpha-adrenergic-inducible expression in cultured neonatal rat myocardial cells.
To study the transcriptional regulatory mechanisms which mediate cardiac-specific and inducible expression during myocardial cell hypertrophy, we have extensively characterized the rat cardiac myosin light-chain-2 (MLC-2) gene as a model system. The MLC-2 gene encodes a relatively abundant contractile protein in slow skeletal and cardiac muscle and is upregulated during in vivo cardiac hypertrophy and alpha-adrenergic-mediated hypertrophy of neonatal rat myocardial cells. In transient expression assays employing a series of MLC-2-luciferase constructs, recent studies have identified a 250-bp fragment which is sufficient for both cardiac-specific and alpha-adrenergic-inducible expression. Within this 250-bp fragment lie three regions (HF-1, HF-2, and HF-3), each greater than 10 bp in length, which are conserved between the chicken and rat cardiac MLC-2 genes, suggesting their potential role in the regulated expression of this contractile protein gene. As assessed by substitution mutations within each of the conserved regions, the present study demonstrates that HF-1 and HF-2 are important in both cardiac-specific and inducible expression, while HF-3 has no detectable role in the regulated expression of the MLC-2 gene in transient expression assays. HF-1 sequences confer both cardiac-specific and inducible expression to a neutral promoter-luciferase construct but have no significant effect in the skeletal muscle or nonmuscle cell contexts. Thus, these studies have identified a new cardiac-specific regulatory element (HF-1) which plays a role in both cardiac-specific and inducible expression during myocardial cell hypertrophy.
Zhu
H
H
Department of Medicine, University of California, San Diego, School of Medicine, La Jolla 92093.
Garcia
A V
AV
Ross
R S
RS
Evans
S M
SM
Chien
K R
KR
D000818:Animals; D000831:Animals, Newborn; D001482:Base Composition; D001483:Base Sequence; D002454:Cell Differentiation; D002478:Cells, Cultured; D015870:Gene Expression; D005796:Genes; D051379:Mice; D008969:Molecular Sequence Data; D009132:Muscles / Q000166:cytology / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009218:Myosins / Q000235:genetics*; D009928:Organ Specificity / Q000235:genetics; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D012045:Regulatory Sequences, Nucleic Acid; D015854:Up-Regulation
D011942:Receptors, Adrenergic, alpha; D009218:Myosins