Cultrone Antonietta, Domínguez Yazmid Reyes, Drevet Christine, Scazzocchio Claudio, Fernández-Martín Rafael
Institut de Génétique et de Microbiologie, Université Paris-Sud, Bâtiment 409, UMR 8621 CNRS, 91405 Orsay Cedex, France.
Mol Microbiol. 2007 Mar;63(6):1577-87. doi: 10.1111/j.1365-2958.2007.05609.x.
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.
在构巢曲霉中，xanA基因编码一种黄嘌呤α-酮戊二酸依赖性双加氧酶，该酶仅存在于真菌界。该基因的5'区域，包括其推定的启动子和开放阅读框的前54个密码子，连同第一个内含子在基因组中被复制。这种复制对应于一个转座子，一种被认为通过滚环机制进行复制转座的真核元件。我们表明，xanA的调控与嘌呤降解途径的其他基因的调控一致，需要特定的UaY转录因子和AreA GATA因子。复制区域的启动子在异位是活跃的，并且难以从复制区域检测到mRNA至少部分是由于无义介导的衰变。比较基因组数据仅与以下假设一致：xanA的5'区域在转座子插入之前就已存在，并且一个“二级转座子”是由其5'端的插入和开放阅读框内预先存在的3'共有序列产生的。有可能提出转座子在启动子改组中的作用，从而在将新基因招募到特定调控回路中的作用。
