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A cDNA from brain of Xenopus laevis coding for a new precursor of thyrotropin‐releasing hormone
Author(s) -
Bulant Mare,
Richter Klaus,
Kuchler Karl,
Kreil Günther
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)80307-3
Subject(s) - xenopus , complementary dna , thyrotropin releasing hormone , hormone , medicine , biology , endocrinology , chemistry , microbiology and biotechnology , biochemistry , gene
Thyrotropin‐releasing hormone (TRH) is found in large amounts in the skin of Xenopus laevis . In this tissue, 3 TRH precursor mRNAs can be detected of which the 2 more expressed encode almost identical proteins. However, Northern blot analysis of TRH precursor mRNAs in the brain or X. leavis revealed the existence of a new mRNA of about 1200 nucleotides which was present along with the larger TRH precursor mRNA identified in the skin. A cloned cDNA of a TRH precursor, corresponding in size to this new mRNA, was isolated and sequenced from a Xenopus brain λgtl 1 library. It encodes a precursor polypeptide which also contains 7 copies of TRH. However, at the amino acid level it differs by about 16% from the corresponding prepro‐TRHs from skin. We have also attempted to characterize the gene encoding this prepro‐TRH from a Xenopus brain. Only the first and part of the second exon could be detected which are separated by an intron containing more than 8000 base pairs. Interestingly, the 5′‐flanking region of this gene does not contain the characteristic promoter elements of the mammalian TRH genes suggesting marked differences in the regulation or their expression.