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Mol Biol Evol. 2011 Jul;28(7):2125-37. doi: 10.1093/molbev/msr035. Epub 2011 Feb 5.

Evolution of nuclear retinoic acid receptor alpha (RARα) phosphorylation sites. Serine gain provides fine-tuned regulation.

Author information

1
IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), Institut National de Sante et de Recherche Medicale (INSERM), U596, Centre National de Recherche Scientifique (CNRS), UMR7104, Université de Strasbourg, 1 rue Laurent Fries, BP 10142, 67404 Illkirch Cedex, France.

Abstract

The human nuclear retinoic acid (RA) receptor alpha (hRARα) is a ligand-dependent transcriptional regulator, which is controlled by a phosphorylation cascade. The cascade starts with the RA-induced phosphorylation of a serine residue located in the ligand-binding domain, S(LBD), allowing the recruitment of the cdk7/cyclin H/MAT1 subcomplex of TFIIH through the docking of cyclin H. It ends by the subsequent phosphorylation by cdk7 of an other serine located in the N-terminal domain, S(NTD). Here, we show that this cascade relies on an increase in the flexibility of the domain involved in cyclin H binding, subsequently to the phosphorylation of S(LBD). Owing to the functional importance of RARα in several vertebrate species, we investigated whether the phosphorylation cascade was conserved in zebrafish (Danio rerio), which expresses two RARα genes: RARα-A and RARα-B. We found that in zebrafish RARαs, S(LBD) is absent, whereas S(NTD) is conserved and phosphorylated. Therefore, we analyzed the pattern of conservation of the phosphorylation sites and traced back their evolution. We found that S(LBD) is most often absent outside mammalian RARα and appears late during vertebrate evolution. In contrast, S(NTD) is conserved, indicating that the phosphorylation of this functional site has been under ancient high selection constraint. This suggests that, during evolution, different regulatory circuits control RARα activity.

PMID:
21297158
DOI:
10.1093/molbev/msr035
[Indexed for MEDLINE]

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