The tightly regulated promoter of the xanA gene of Aspergillus nidulans is included in a helitron.
In Aspergillus nidulans the xanA gene codes for a xanthine alpha-ketoglutarate-dependent dioxygenase, an enzyme only present in the fungal kingdom. The 5' region of this gene, including its putative promoter and the first 54 codons of the open reading frame, together with the first intron is duplicated in the genome. This duplication corresponds to a helitron, a eukaryotic element proposed to transpose replicatively by the rolling circle mechanism. We show that the regulation of xanA conforms to that of other genes of the purine degradation pathway, necessitating the specific UaY transcription factor and the AreA GATA factor. The promoter of the duplicated region is active ectopically and the difficulty in detecting an mRNA from the duplicated region is at least partially due to nonsense-mediated decay. Comparative genomic data are only consistent with the hypothesis that the 5' region of xanA pre-existed the helitron insertion, and that a 'secondary helitron' was generated from an insertion 5' to it and a pre-existing 3' consensus sequence within the open reading frame. It is possible to propose a role of helitrons in promoter shuffling and thus in recruiting new genes into specific regulatory circuits.
Cultrone
Antonietta
A
Institut de Génétique et de Microbiologie, Université Paris-Sud, Bâtiment 409, UMR 8621 CNRS, 91405 Orsay Cedex, France.
Domínguez
Yazmid Reyes
YR
Drevet
Christine
C
Scazzocchio
Claudio
C
Fernández-Martín
Rafael
R
D001233:Aspergillus nidulans / Q000235:genetics / Q000378:metabolism*; D004251:DNA Transposable Elements; D049308:Dioxygenases / Q000235:genetics* / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D005800:Genes, Fungal; D011401:Promoter Regions, Genetic / Q000235:genetics*; D014970:Xanthines / Q000378:metabolism
D004251:DNA Transposable Elements; D005656:Fungal Proteins; D014970:Xanthines; D049308:Dioxygenases; C503093:xanthine dioxygenase, Aspergillus nidulans