Donoghue M, Ernst H, Wentworth B, Nadal-Ginard B, Rosenthal N
Department of Biochemistry, Boston University School of Medicine, Massachusetts 02118.
Genes Dev. 1988 Dec;2(12B):1779-90. doi: 10.1101/gad.2.12b.1779.
Two skeletal myosin light chains, MLC1 and MLC3, are generated from a single gene by transcription from two different promoters and alternate splicing of the pre-mRNAs. To define DNA sequences involved in MLC transcriptional control, we constructed a series of plasmid vectors in which segments of the rat MLC locus were linked to a CAT gene and assayed for expression in muscle and nonmuscle cells. Whereas sequences proximal to the two MLC promoters do not appear to contain tissue-specific regulatory elements, a 0.9-kb DNA segment, located greater than 24 kb downstream of the MLC1 promoter, dramatically increases CAT gene expression in differentiated myotubes but not in undifferentiated myoblasts or nonmuscle cells. The ability of this segment to activate gene expression to high levels, in a distance-, promoter-, position-, and orientation-independent way, defines it as a strong muscle-specific enhancer element.
两条骨骼肌肌球蛋白轻链，即MLC1和MLC3，由单个基因通过来自两个不同启动子的转录以及前体mRNA的可变剪接产生。为了确定参与MLC转录调控的DNA序列，我们构建了一系列质粒载体，其中大鼠MLC基因座的片段与CAT基因相连，并检测其在肌肉细胞和非肌肉细胞中的表达。虽然两个MLC启动子近端的序列似乎不包含组织特异性调控元件，但一个位于MLC1启动子下游超过24 kb处的0.9 kb DNA片段，能显著增加分化肌管中CAT基因的表达，但在未分化的成肌细胞或非肌肉细胞中则不然。该片段以一种与距离、启动子、位置和方向无关的方式将基因表达激活至高水平的能力，将其定义为一个强大的肌肉特异性增强子元件。
