Functionality versus strength -- has functional selection taken place in the case of the ecdysteroid receptor response element?.
Acta Biochim Pol
; 49(3): 747-56, 2002.
Article
em En
| MEDLINE
| ID: mdl-12422244
ABSTRACT
Nuclear receptors are ligand-dependent transcription factors responsible for controlling differentiation, growth and development of higher eukaryotes. Three amino acids within the recognition alpha-helix of the DNA-binding domain of the nuclear receptors constitute the so-called "P-box" which determines response element specificity. In the ultraspiracle (Usp) protein, which together with EcR forms the heterodimeric ecdysone receptor, the P-box residues are E19, G20 and G23. Substitution of E19, the most characteristic amino acid for estrogen receptor-like P-boxes, with alanine showed that the mutation did not appreciably alter the affinity of the wild-type Usp DNA-binding domain (UspDBD(WT)) for a probe containing natural ecdysone response element (hsp27(wt)). Since in many cases E19 contacts a G/C base pair in position -4, which is absent in hsp27(wt), we analysed the interaction of UspDBD(WT), E19A and other P-box region mutants with the hsp27(wt) derivative which contains a G/C instead of an T/A base pair in position -4. UspDBD(WT) exhibited higher affinity for this element than for hsp27(wt). Moreover, a different interaction pattern of P-box region mutants was also observed. Thus we conclude that the E19 residue of UspDBD is not involved in any hsp27(wt) sequence-discerning contacts. However, substitution of the hsp27(wt) T/A base pair in position -4 with G/C generates target sequence with distinct functional characteristics and possibly with a new specificity. These results could serve as a basis for understanding the role of the presence of a T/A or G/C base-pair in the position -4 in the two types of ecdysone response elements found in nature.
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Base de dados:
MEDLINE
Assunto principal:
Receptores de Esteroides
/
Elementos de Resposta
/
Proteínas de Ligação a DNA
Limite:
Animals
Idioma:
En
Revista:
Acta Biochim Pol
Ano de publicação:
2002
Tipo de documento:
Article
País de afiliação:
Polônia