Libri D, Lemonnier M, Meinnel T, Fiszman M Y
Département de Biologie Moléculaire, Institut Pasteur, Paris, France.
J Biol Chem. 1989 Feb 15;264(5):2935-44.
A chicken genomic DNA library was screened with a full length cDNA corresponding to the beta subunit of smooth muscle tropomyosin. When hybridized with RNAs isolated from various tissues, this cDNA recognizes two mRNA species: one of 1.3 kilobase pairs present only in smooth muscle and one of 1.6 kilobase pairs present only in skeletal muscle. Two overlapping recombinant phages were shown to contain the entire locus and were further characterized. This locus contains 11 exons and spans approximately 13 kilobase pairs. Exon 1 (amino acids 1-38) contains the 5'-untranslated region which is common to the two mRNAs. Exons 6 (amino acids 189-213) and 11 (amino acids 258-284) contain sequences which are present exclusively in the 1.3-kilobase pair smooth muscle mRNA while exons 7 and 10, which code for an analogous region, contain sequences which are present exclusively in the 1.6-kilobase pair skeletal muscle mRNA (exons 10 and 11 also contain the entire 3'-untranslated regions of the corresponding mRNAs). Other exons, 2 to 5 (amino acids 39-188) and 8 and 9 (amino acids 214-257), contain sequences which are present in both mRNAs. Our results indicate that both the smooth and skeletal beta-tropomyosin mRNAs are derived from transcripts of a single gene with a unique promoter by a differential splicing mechanism.
用与平滑肌原肌球蛋白β亚基对应的全长cDNA筛选鸡基因组DNA文库。当与从各种组织中分离的RNA杂交时，该cDNA识别两种mRNA：一种1.3千碱基对的仅存在于平滑肌中，另一种1.6千碱基对的仅存在于骨骼肌中。两个重叠的重组噬菌体被证明包含整个基因座并进一步进行了表征。该基因座包含11个外显子，跨度约为13千碱基对。外显子1（氨基酸1 - 38）包含两种mRNA共有的5'-非翻译区。外显子6（氨基酸189 - 213）和11（氨基酸258 - 284）包含仅存在于1.3千碱基对平滑肌mRNA中的序列，而编码类似区域的外显子7和10包含仅存在于1.6千碱基对骨骼肌mRNA中的序列（外显子10和11还包含相应mRNA的整个3'-非翻译区）。其他外显子，2至5（氨基酸39 - 188）以及8和9（氨基酸214 - 257），包含两种mRNA中都存在的序列。我们的结果表明，平滑肌和骨骼肌的β-原肌球蛋白mRNA均通过差异剪接机制源自具有独特启动子的单个基因的转录本。
