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Characterization of a cDNA defining a gene family encoding TM30p1, a human fibroblast tropomyosin
Abstract:
We have isolated a cDNA that contains the complete coding sequence of a 3.0 X 10(3) base human fibroblast mRNA together with a large part of its 3' untranslated sequence. The deduced protein sequence is very similar if not identical to the sequence of horse platelet tropomyosin, a 247 amino acid protein. In vitro translation of an SP6 transcript of this cDNA reveals that the protein product of the 3.0 X 10(3) base mRNA is TM30p1, one of the five proteins in human fibroblasts that have been shown to possess the physical and chemical characteristics of tropomyosin. This mRNA is encoded by a gene family that consists of a functional gene and multiple RNA-copy pseudogenes. This family of sequences is distinct from the gene family encoding TM30nm, a cytoskeletal tropomyosin very similar in electrophoretic mobility to TM30p1, but which shows significant differences in primary structure.
Insights
Researchers identified a human fibroblast messenger RNA (mRNA) encoding TM30p1, a tropomyosin protein. This mRNA is part of a gene family distinct from that of cytoskeletal tropomyosin TM30nm.
Area of Science:
- Molecular Biology
- Genetics
- Protein Chemistry
Background:
- Tropomyosin proteins are crucial components in various cellular functions.
- Human fibroblasts express multiple tropomyosin isoforms, including TM30p1 and TM30nm, which share similarities but have distinct structures.
Purpose of the Study:
- To isolate and characterize the cDNA encoding the human fibroblast tropomyosin TM30p1.
- To elucidate the genetic origin and relationship of the TM30p1 mRNA.
- To differentiate the TM30p1 gene family from that of TM30nm.
Main Methods:
- Isolation of a complementary DNA (cDNA) containing the full coding sequence and partial 3' untranslated region of a human fibroblast mRNA.
- In vitro translation of an SP6 transcript derived from the isolated cDNA.
- Sequence comparison with known tropomyosin proteins and gene families.
Main Results:
- A cDNA encoding a 247 amino acid protein, highly similar to horse platelet tropomyosin, was isolated.
- In vitro translation confirmed the protein product as TM30p1.
- The TM30p1 mRNA is encoded by a gene family comprising a functional gene and pseudogenes, distinct from the TM30nm gene family.
Conclusions:
- The study successfully identified and characterized the cDNA for human fibroblast tropomyosin TM30p1.
- TM30p1 represents a distinct tropomyosin isoform encoded by a separate gene family.
- This work clarifies the genetic basis and molecular identity of TM30p1 in human fibroblasts.