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KMID : 0578319920020010067
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Molecules and Cells
1992 Volume.2 No. 1 p.67 ~ p.74
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Identification of a Cis-acting Element of the Quail East Troponin I Gene
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Lee Young-Won
Charles P. Jr. Emerson
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Abstract
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DNA transfection studies of deletion mutants of the quail fast troponin I gene have localized a 510-bp cis-acting enhancer element spanning +478 through +996 within the TnI first intron. This element controls the myofiber-specific expression of the TnI gene promoter and also the myofiber-specific expression of the heterologous promoter of herpes simplex virus thymidine kinase (TK) gene. Sequence comparisons of this enhancer element with other regulatory motifs in enhancer elements of muscle and non-muscle genes reveal that the enhancer contains consensus binding motifs for several important regulatory proteins including CArG, AP-2 and MyoDl. Deletion analysis and site-directed mutagenesis of the MyoD1 binding site show that CArG, AP-2 and MyoD1 binding motifs are necessary for the myofiber-specific expression of the TnI gene. Gel shift analyses show that nuclear extracts of I0Tl/2 fibroblasts, myoblasts and myofrbers have binding activities to CArG and AP-2 binding motifs within the TnI enhancer element. Their binding activities to an oligodeoxynucleotide of the MyoD1 binding site are also detected in myoblasts and myofibers, but not in IOTl/2 cells. These studies, therefore, indicate that the TnI enhancer is composed of multiple regulatory motifs that interact with specific DNA binding factors in lOTl/2 cells and additional factors in muscle cells. These results suggest that similar enhancer motifs and DNA binding factors coordinate the transcriptional activation of muscle genes during myoblast differentiation.
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KEYWORD
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