
Structural analysis of the entire proopiomelanocortin gene of Xenopus laevis
Author(s) -
DEEN Peter M. T.,
TERWEL Dick,
BUSSEMAKERS Marion J. M.,
ROUBOS Eric W.,
MARTENS Gerard J. M.
Publication year - 1991
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1991.tb16265.x
Subject(s) - xenopus , proopiomelanocortin , biology , gene , promoter , genetics , intron , regulatory sequence , 5' flanking region , microbiology and biotechnology , regulation of gene expression , gene expression
In the pars intermedia of the pituitary the prohormone proopiomelanocortin (POMC) is tissue‐specifically processed to, among other peptides, α‐melanotropin (αMSH). In the South African clawed toad Xenopus laevis this hormone mediates the process of background adaptation: release of α‐MSH causes darkening of the animal, while inhibition of α‐MSH release results in a pale toad. Elevated release of α‐MSH coincides with a higher rate of POMC gene transcription. The present study aims to find possible transcriptional regulatory elements in the Xenopus POMC gene. For that purpose the complete nucleotide sequence of the POMC gene and its 5′‐ and 3′‐flanking regions were determined and analyzed. The Xenopus POMC gene promoter contains several regions which may be regulatory DNA elements in view of their similarity with corresponding regions of mammalian POMC gene promoters. In the rat POMC gene promoter, many of these regions represent protein‐binding sequences. Besides the promoter sequence and the protein‐coding sequences, no other segments with significant identity between the Xenopus and human POMC genes were found. Intron A of the Xenopus POMC gene contains a simple sequence, (TATC) 76 , and a JH12 repetitive element, while the 3′‐flanking region contains a repetitive‐ Eco RI‐monomer‐2 element. Comparison of the JH12 sequence of the POMC gene with JH12 sequences from other Xenopus genes revealed a 335‐bp consensus sequence which is flanked by a 30‐bp inverted repeat. This JH12 consensus sequence is significantly larger than the previously reported JH12 core region. Alignment of intron B of the Xenopus POMC gene with database sequences revealed a consensus sequence of a novel Xenopus repetitive element of 330 bp flanked by a nearly perfect inverted repeat. indicating that this element may be a transposonlike element.