Hoyer L L, Scherer S, Shatzman A R, Livi G P
Human Genome Center, Lawrence Berkeley Laboratory, Berkeley, California 94720.
Mol Microbiol. 1995 Jan;15(1):39-54. doi: 10.1111/j.1365-2958.1995.tb02219.x.
Transfer of budding Candida albicans yeast cells from the rich, complex medium YEPD to the defined tissue culture medium RPMI 1640 (RPMI) at 37 degrees C and 5% CO2 causes rapid onset of hyphal induction. Among the genes induced under these conditions are hyphal-specific genes as well as genes expressed in response to changes in temperature, CO2 and specific media components. A cDNA library constructed from cells incubated for 20 min in RPMI was differentially screened with yeast (YEPD)- and hyphal (RPMI)-specific probes resulting in identification of a gene expressed in response to culture conditions but not regulated by the yeast-hyphal transition. The deduced gene product displays significant identity to Saccharomyces cerevisiae alpha-agglutinin, encoded by AG alpha 1, an adhesion glycoprotein that mediates mating of haploid cells. The presence of this gene in C. albicans is curious since the organism has not been observed to undergo meiosis. We designate the C. albicans gene ALS1 (for agglutinin-like sequence). While the N- and C-termini of the predicted 1260-amino-acid ALS1 protein resemble those of the 650-amino-acid AG alpha 1, ALS1 contains a central domain of tandem repeats consisting of a highly conserved 36-amino-acid sequence not present in AG alpha 1. These repeats are also present on the nucleotide level as a highly conserved 108 bp motif. Southern and Northern blot analyses indicate a family of C. albicans genes that contain the tandem repeat motif; at least one gene in addition to ALS1 is expressed under conditions similar to those for ALS1 expression. Genomic Southern blots from several C. albicans isolates indicate that the number of copies of the tandem repeat element in ALS1 differs across strains and, in some cases, between ALS1 alleles in the same strain, suggesting a strain-dependent variability in ALS1 protein size. Potential roles for the ALS1 protein are discussed.
将出芽的白色念珠菌酵母细胞从富含多种成分的复杂培养基YEPD转移至特定的组织培养基RPMI 1640（RPMI）中，于37℃和5%二氧化碳条件下培养，会迅速引发菌丝诱导。在这些条件下诱导表达的基因中，既有菌丝特异性基因，也有因温度、二氧化碳及特定培养基成分变化而表达的基因。用酵母（YEPD）特异性探针和菌丝（RPMI）特异性探针，对在RPMI中孵育20分钟的细胞构建的cDNA文库进行差异筛选，从而鉴定出一个对培养条件有反应但不受酵母 - 菌丝转变调控的基因。推导的基因产物与酿酒酵母α - 凝集素具有显著同源性，酿酒酵母α - 凝集素由AGα1编码，是一种介导单倍体细胞交配的黏附糖蛋白。白色念珠菌中存在该基因很是奇特，因为尚未观察到该生物体进行减数分裂。我们将白色念珠菌的这个基因命名为ALS1（凝集素样序列）。预测的1260个氨基酸的ALS1蛋白的N端和C端与650个氨基酸的AGα1相似，但ALS1包含一个由高度保守的36个氨基酸序列组成的串联重复中央结构域，AGα1中不存在该序列。这些重复序列在核苷酸水平上也以高度保守的108 bp基序形式存在。Southern和Northern印迹分析表明，白色念珠菌中有一个包含串联重复基序的基因家族；除ALS1外，至少还有一个基因在与ALS1表达相似的条件下表达。来自多个白色念珠菌分离株的基因组Southern印迹表明，ALS1中串联重复元件的拷贝数在不同菌株间存在差异，在某些情况下，同一菌株的ALS1等位基因之间也存在差异，这表明ALS1蛋白大小存在菌株依赖性变异。文中还讨论了ALS1蛋白的潜在作用。
