Structural organization of the 5' region of the human thyroglobulin gene

TARGOVNIK , HÉCTOR MANUEL; POHL, VIVIANE; CHRISTOPHE, DANIEL; CABRER, BARTOLOME; BROCAS, HUGUETTE; VASSART, GILBERT

FEBS JOURNAL

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 1984 vol. 141 p. 271 - 277

1742-464X

Sequence analyses of bovine and human thyroglobulin (Tg) cDNA have demonstrated that the 5´ region of the mRNA encodes a domain responsible for thyroid hormone synthesis and exhibits striking internal repetition. Knowledge of the organization of the corresponding chromosomal DNA region would provide insight as to how such a structure has evolved. A human genomic DNA library was screened by hybridization in situ, using a bovine Tg cDNA probe corresponding to 2.8 x 10´ base pairs at the 5´ end of the mRNA. Out of 3 x l05 phage plaques, four were scored as positive and yielded three different phages containing thyroglobulin sequences. Selected human Tg cDNA probes were used to order the phages and to identify overlapping regions. Electron microscopy of hybrids between human Tg mRNA and the phage DNA was performed to determine the intron/exon organization of this region. The following conclusions were reached. (a) About 4 x 10, base pairs corresponding to the 5´ region of the gene have been isolated as three overlapping recombinant phages. (b) The three phages cover altogether 2.9 x 103 base pairs of exonic sequence at the 5´ end of the mRNA. (c) Out of the 11 exons identified in this region, 9 were of a size similar to that of the 3´ exons characterized previously (200 base pairs); exons 9 (1.12 x lo3 base pairs) and 10 (0.56 x l03 base pairs) were exceptions to this rule. (d) The phage nearest the 5´ end contains about 9 x 103 base pairs of sequence located upstream from the gene. The avalability of clones covering the region upstream from the thyroglobin gene will provide the basis for the identification of sequences involved in its transcriptional control by thyroid-stimulating hormone (thyrotropin).