title: Reprogramming of myosin light chain 1/3 expression in muscle heterokaryons.
abstract: Fast myosin light chain (MLC) 1/3 is one of the few genes which regulates transcript production at both transcriptional and post-transcriptional levels, utilizing two functionally distinct promoters coupled with alternatively spliced exons. The transcriptional process controlling expression from this single gene locus is developmentally regulated, such that MLC 1 precedes MLC 3 during myogenesis. Results from our RNA analyses demonstrate that in differentiated rat L6E9 muscle, MLC 3 is the sole isoform expressed from the MLC 1/3 locus. However, we also show that by generating rat L6E9:mouse C2 muscle heterokaryons, MLC 1 expression from the L6E9 MLC locus can be induced. In addition to novel rat MLC 1 expression in the C2:L6E9 heterokaryons, we show that the synthesis profile of rat MLC 3 mRNA is also altered relative to L6E9 muscle cultured alone. Additional experiments demonstrate that the reprogramming of rat MLC 1 and 3 expression in the muscle heterokaryons requires that C2 and L6E9 nuclei be contained within a common cytoplasm. These results demonstrate that expression from the MLC 1/3 gene is "plastic," and is not under the control of a strict developmental program but, rather, can be modified by the environmental milieu.
authors.affiliation: Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Ohio 45267-0524.
authors.forename: L
authors.initials: L
authors.lastname: Pajak
authors.forename: M
authors.initials: M
authors.lastname: Mariappan
authors.forename: D F
authors.initials: DF
authors.lastname: Wieczorek
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002478:Cells, Cultured; D005333:Fetus; D015870:Gene Expression; D005796:Genes; D051379:Mice; D008969:Molecular Sequence Data; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology*; D009218:Myosins / Q000235:genetics*; D009693:Nucleic Acid Hybridization; D015345:Oligonucleotide Probes; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D014158:Transcription, Genetic
chemical_list: D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D012313:RNA; D009218:Myosins