Gow A, Friedrich V L, Lazzarini R A
Brookdale Center for Molecular Biology, Mount Sinai Medical Center, New York 10029-6574.
J Cell Biol. 1992 Nov;119(3):605-16. doi: 10.1083/jcb.119.3.605.
The DNA sequence between position +36 and -1907 of the murine myelin basic protein gene contains the enhancer and promoter elements necessary for abundant and cell specific expression in transgenic mice. Surprisingly, the pattern of expression promoted by this DNA fragment is a subset of that exhibited by the endogenous myelin basic protein (MBP) gene. Fusion genes prepared with this promoter/enhancer and a Lac Z reporter gene are expressed only in oligodendrocytes and not in Schwann cells, whereas the endogenous MBP gene is expressed in both cell types. The level of transgene expression measured by nuclear run-on experiments is very substantial and rivals that of the endogenous MBP gene. Furthermore, this 1.9-kb DNA fragment directs transcription on the same (or very similar) developmental schedule as the endogenous gene. These results indicate that the MBP promoter/enhancer sequences are at least tripartite: a core promoter, the oligodendrocyte enhancer elements, and a third component that either expands the specificity of the oligodendrocyte enhancer to include Schwann cells or acts independently to specifically stimulate transcription in Schwann cells.
小鼠髓鞘碱性蛋白基因中位于+36至-1907位置之间的DNA序列包含在转基因小鼠中实现丰富且细胞特异性表达所必需的增强子和启动子元件。令人惊讶的是，该DNA片段所促进的表达模式只是内源性髓鞘碱性蛋白（MBP）基因所呈现模式的一个子集。用该启动子/增强子与Lac Z报告基因制备的融合基因仅在少突胶质细胞中表达，而在施万细胞中不表达，而内源性MBP基因在这两种细胞类型中均有表达。通过核转录实验测量的转基因表达水平非常可观，可与内源性MBP基因相媲美。此外，这个1.9kb的DNA片段与内源性基因在相同（或非常相似）的发育时间表上指导转录。这些结果表明，MBP启动子/增强子序列至少由三部分组成：一个核心启动子、少突胶质细胞增强子元件，以及第三个成分，它要么将少突胶质细胞增强子的特异性扩展到包括施万细胞，要么独立发挥作用以特异性刺激施万细胞中的转录。
