Structural heterogeneity of human thyroglobulin in relation to its messenger RNA maturation

One human thyroglobulin cDNA clone present 192 nucleotides deletion which correspond to 64 amino-acid deletion on the protein molecule. We show that this fact figure the exon loss on the mRNA molecule using as template during cDNA synthesis by comparison between mRNA and genomic DNA nucleotide sequences. Different possibility can explain this fact. We retain mainly mistake in mRNA maturation fidelity. This type of event is not an exception and can be an explanation for some pathologies.     

Reverse transcription of thyroglobulin 33-S mRNA.

Bovine thyroglobulin 33-S mRNA has been used as a template for the synthesis of a complementary DNA, using RNA-directed DNA polymerase from the avian myeloblastosis virus. The yield of the reaction was relatively poor and the size of the cDNA did not exceed 10 S. Nevertheless, a copy of high specific radioactivity (approximately 10(7) counts. min-1 microgram-1) could be obtained which hybridized specifically back to its template with an rot1/2 value about 5 times higher than that observed in hybridizations between hemoglobin mRNA (alpha + beta chain) and hemoglobin cDNA. This suggests that thyroglobulin mRNA does not contain extensive internal repetitive sequences. Quantification of thyroglobulin mRNA sequences among various RNA preparations from the beef thyroid was performed using cDNA/RNA hybridizations in RNA excess. The results confirmed that thyroglobulin mRNA represents the large majority of mRNA in membrane-bound polysomes and indicated the virtual absence of thyroglobulin sequences on free polyosomes. The cDNA transcribed from mRNA of bovine origin hybridized efficiently with thyroid RNA from goats, dogs and humans. Although the heterologuous hybrids exhibited the expected decrease in thermal stability, the bovine cDNA provides an appropriate probe for studies dealing with the expression of the thyroglobulin gene in various mammals including man.     

Restriction mapping of synthetic thyroglobulin structural gene as a means of investigating thyroglobulin structure

Bovine 33 S thyroglobulin mRNA was reverse transcribed into double-stranded DNA under conditions allowing the synthesis of a complete 8 kilobase pair copy. A physical map of the resulting synthetic thyroglobulin structural gene was constructed using six restriction endonucleases. The following conclusions could be drawn: (i) the polypeptide chains in thyroglobulin subunits are identical; (ii) thyroglobulin is composed of a major class of molecules sharing the same primary structure; (iii) there is no evidence for precise internal repetition in the structure of thyroglobulin subunits.     

Isolation and characterization of cDNA for chicken muscle adenylate kinase

A cDNA clone for muscle adenylate kinase was isolated from a cDNA library of chick skeletal muscle poly(A)+ RNA, and the DNA sequence was determined. The cDNA insert had 854 nucleotides, which consisted of the 5'-untranslated sequence of 57 nucleotides, the sequence of 582 nucleotides coding for 194 amino acids, and the 3'-untranslated sequence of 163 nucleotides and the poly(A) tail of 52 nucleotides. The amino acid sequence predicted from the nucleotide sequence was highly homologous with the reported sequences of human, calf, porcine, and rabbit muscle adenylate kinases. RNA blot analysis of poly(A)+ RNA from various chicken tissues revealed a single species of mRNA of approximately 850 nucleotides and its tissue-specific distribution. The induction of muscle adenylate kinase mRNA synthesis during the chick embryogenesis was also demonstrated by the blot analysis. Southern blot analysis indicated a single gene for muscle adenylate kinase in the chicken genome.