Hall Charles, Dietrich Fred S
Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Genetics. 2007 Dec;177(4):2293-307. doi: 10.1534/genetics.107.074963.
The synthesis of biotin, a vitamin required for many carboxylation reactions, is a variable trait in Saccharomyces cerevisiae. Many S. cerevisiae strains, including common laboratory strains, contain only a partial biotin synthesis pathway. We here report the identification of the first step necessary for the biotin synthesis pathway in S. cerevisiae. The biotin auxotroph strain S288c was able to grow on media lacking biotin when BIO1 and the known biotin synthesis gene BIO6 were introduced together on a plasmid vector. BIO1 is a paralog of YJR154W, a gene of unknown function and adjacent to BIO6. The nature of BIO1 illuminates the remarkable evolutionary history of the biotin biosynthesis pathway in S. cerevisiae. This pathway appears to have been lost in an ancestor of S. cerevisiae and subsequently rebuilt by a combination of horizontal gene transfer and gene duplication followed by neofunctionalization. Unusually, for S. cerevisiae, most of the genes required for biotin synthesis in S. cerevisiae are grouped in two subtelomeric gene clusters. The BIO1-BIO6 functional cluster is an example of a cluster of genes of "dispensable function," one of the few categories of genes in S. cerevisiae that are positionally clustered.
生物素是许多羧化反应所需的一种维生素，其合成在酿酒酵母中是一个可变性状。许多酿酒酵母菌株，包括常见的实验室菌株，仅含有部分生物素合成途径。我们在此报告了酿酒酵母生物素合成途径第一步的鉴定。当将BIO1和已知的生物素合成基因BIO6一起导入质粒载体时，生物素营养缺陷型菌株S288c能够在缺乏生物素的培养基上生长。BIO1是YJR154W的旁系同源基因，YJR154W是一个功能未知且与BIO6相邻的基因。BIO1的性质揭示了酿酒酵母生物素生物合成途径显著的进化历史。该途径似乎在酿酒酵母的一个祖先中丢失，随后通过水平基因转移和基因复制并继之以新功能化的组合得以重建。不同寻常的是，对于酿酒酵母来说，其生物素合成所需的大多数基因聚集在两个亚端粒基因簇中。BIO1 - BIO6功能簇是“可有可无功能”基因簇的一个例子，是酿酒酵母中少数按位置聚集的基因类别之一。
