The chicken tropomyosin 1 gene generates nine mRNAs by alternative splicing.
Skeletal muscle beta-tropomyosin, smooth muscle alpha-tropomyosin, and a low molecular weight fibroblast tropomyosin are generated by alternatively splicing RNA transcripts of the chicken tropomyosin 1 (TM 1) gene (Forry-Schaudies, S., Maihle, N. J., and Hughes, S. H. (1990) J. Mol. Biol. 211; 321-330). Two novel tropomyosin cDNAs that derive from mRNAs of the TM 1 gene have been isolated from a chicken embryo brain cDNA library. Brain cDNA BRT-1 is 2.2 kilobases in length and encodes 283 amino acids. It is identical to skeletal muscle beta-tropomyosin from amino acids 1 to 258. The sequence 3' of this point is unique to BRT-1; a comparison to genomic sequence indicates that a new carboxyl-terminal exon is used to generate this sequence. 1.4-kilobase brain cDNA BRT-2 contains sequences found in both fibroblast cDNA FT-beta (5'-end) and skeletal muscle cDNA SKT-beta (3'-end). RNase and S1 nuclease assays using RNA samples from leg muscle, gizzard, fibroblasts, and brain indicate that the TM 1 gene expresses four additional tropomyosin RNAs by alternately splicing previously characterized exons. These results demonstrate that the chicken TM 1 gene encodes nine tropomyosin RNAs through the use of two promoters, two internal exons that are mutually exclusive, and three 3'-exons. Implications for the regulation of alternative splicing are discussed.
Forry-Schaudies
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ABL-Basic Research Program, National Cancer Institute-Frederick Cancer Research and Development Center, Maryland 21702-1201.
Hughes
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D001921:Brain / Q000502:physiology; D002645:Chickens; D004247:DNA / Q000235:genetics; D015870:Gene Expression; D005796:Genes; D008969:Molecular Sequence Data; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics*; D014335:Tropomyosin / Q000235:genetics*
D012333:RNA, Messenger; D014335:Tropomyosin; D004247:DNA