Repression of the cardiac myosin light chain-2 gene in skeletal muscle requires site-specific association of antithetic regulator, Nished, and HDACs

To investigate the developmental, physiological and pathophysiological roles of human cardiac myosin light-chain 1 (LC1s), we developed two novel monoclonal antibodies (KA1 and KB1) against human cardiac LC1s and examined LC1s in normal and pathological hearts immunohistochemically. KA1 and KB1 were specific only for atrial LC1 (ALC1) and for both ALC1 and ventricular LC1 (VLC1), respectively, in human hearts. Among human tissues tested, including skeletal muscle, vascular smooth muscle, and liver, KA1 did not crossreact with proteins in any other tissues than atria, whereas KB1 crossreacted with the slow-type LC1 of skeletal muscle. Among adult mammalian hearts of several other species including pig, dog, hamster, and rat, KA1 and KB1 crossreacted only with ALC1 and with both ALC1 and VLC1, respectively. ALC1 was strongly and uniformly observed in human fetal atria and ventricles and in normal adult human atria, but sporadically in normal adult human ventricles. In the overloaded ventricle (dilated cardiomyopathy), ALC1 was highly augmented but not uniform. These results suggest that the fetal VLC1 is immunohistochemically identical to the adult type of ALC1 and that ALC1 is expressed homogeneously in human fetal ventricles and sporadically in normal adult ventricles, and is re-expressed heterogeneously and in an increased amount in the overloaded ventricle.

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Amino acid sequence of rabbit ventricular myosin light chain-2: Identity with the slow skeletal muscle isoform

Bioscience Reports ◽

10.1007/bf01114760 ◽

1986 ◽

Vol 6 (7) ◽

pp. 655-661 ◽

Cited By ~ 17

Author(s):

John H. Collins ◽

Janet L. Theibert ◽

Luciano Dalla Libera

Keyword(s):

Skeletal Muscle ◽

Amino Acid ◽

Light Chain ◽

Myosin Light Chain ◽

Strong Support ◽

Sequence Information ◽

Myosin Isoforms ◽

Amino Acid Residues ◽

Myosin Light Chain 2 ◽

Muscle Types

Many studies have established a correlation of differences in the activities of various muscle types with differences in the expression of myosin isoforms. In this paper we report the sequence determination of myosin light chain-2 from rabbit slow skeletal (LC2s) and ventricular (LC2v) nmscles. We sequenced tryptic peptides from LC2v which account for all except a few terminal amino acid residues. The major part (87 residues) of the rabbit LC2s sequence, obtained from tryptic and cyanogen bromide (CNBr) peptides, was found to be identical to rabbit LC2v. Our results provide the first sequence information on LC2s from any species, and lend strong support to the hypothesis that LC2s and LC2v are identical. Comparisons of rabbit LC2v and LC2s with rabbit LC2f (from fast skeletal muscle), and also with chicken LC2f and LC2v, show clearly that LC2s and LC2v from mammalian and avian species are more closely related to each other than they are to LC2f isoforms from the same species.

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A single transcription factor binds to two divergent sequence elements with a common function in cardiac myosin light chain-2 promoter.

Molecular and Cellular Biology ◽

10.1128/mcb.12.3.1107 ◽

1992 ◽

Vol 12 (3) ◽

pp. 1107-1116 ◽

Cited By ~ 16

Author(s):

P Qasba ◽

E Lin ◽

M D Zhou ◽

A Kumar ◽

M A Siddiqui

Keyword(s):

Transcription Factor ◽

Gene Transcription ◽

Light Chain ◽

Myosin Light Chain ◽

Cardiac Myosin ◽

Divergent Sequence ◽

Specific Element ◽

Myosin Light Chain 2 ◽

Sequence Elements ◽

Gel Shift

The cardiac myosin light chain-2 (MLC-2) gene promoter contains several positive and negative cis-acting sequences that are involved in the regulation of its expression. We describe here the properties of two activator sequences, elements A and P, and their DNA-binding factors (ABFs). Element A (CCAAAAGTGG), located at -61, has homology with the evolutionarily conserved sequence CC(A/T)6GG, present in the genes of many contractile proteins. Element P (TAACCTTGAAAGC), located 114 bp upstream of element A, is conserved in both chicken and rat cardiac MLC-2 gene promoters. Deletion mutagenesis demonstrated that these two elements are involved in the positive regulation of MLC-2 gene transcription. At least two sequence-specific element A-binding proteins, ABF-1 and ABF-2, were identified by gel shift analysis of the fractionated cardiac nuclear proteins. ABF-1 binds to element A with strict dependence on the internal element A sequence AAAAGT. In contrast, ABF-2 exhibits a relaxed sequence requirement, as it recognizes the consensus CArG and CCAAT box sequences as well. ABF-2 also recognizes the distal element P despite the fact that the sequences of elements A and P are divergent. DNase I footprinting, methylation interference, and gel shift analyses demonstrated unequivocally that the element A-DNA affinity-purified protein ABF-2 binds to element P with sequence specificity. Since both elements A and P play a positive regulatory role in MLC-2 gene transcription and bind to a single protein (ABF-2), it would appear that ABF-2 is a key transcription factor with the ability to recognize divergent sequence elements involved in a common regulatory pathway during myogenesis.

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