Department of Biomedical Sciences, Chung Shan Medical University, No, 110, Sec, 1, Jianguo N, Road, Taichung City 40201, Taiwan.
J Biomed Sci. 2013 Dec 20;20(1):97. doi: 10.1186/1423-0127-20-97.
CDC4, which encodes an F-box protein that is a member of the Skp1-Cdc53/Cul1-F-box (SCF) ubiquitin E3 ligase, was initially identified in the budding yeast Saccharomyces cerevisiae as an essential gene for progression through G1-S transition of the cell cycle. Although Candida albicans CDC4 (CaCDC4) can release the mitotic defect caused by the loss of CDC4 in S. cerevisiae, CaCDC4 is nonessential and suppresses filamentation.
To further elucidate the function of CaCDC4, a C. albicans strain, with one CaCDC4 allele deleted and the other under the repressible C. albicans MET3 promoter (CaMET3p) control, was made before introducing cassettes capable of doxycycline (Dox)-induced expression of various C. albicans Cdc4 (CaCdc4) domains. Cells from each strain could express a specific CaCdc4 domain under Dox-induced, but CaMET3-CaCDC4 repressed conditions. Cells expressing domains without either the F-box or WD40-repeat exhibited filamentation and flocculation similarly to those lacking CaCDC4 expression, indicating the functional essentiality of the F-box and WD40-repeat. Notably, cells expressing the N-terminal 85-amino acid truncated CaCdc4 partially reverse the filament-to-yeast and weaken the ability to flocculate compared to those expressing the full-length CaCdc4, suggesting that N-terminal 85-amino acid of CaCdc4 regulates both morphogenesis and flocculation.
The F-box and the WD40-repeat of CaCdc4 are essential in inhibiting yeast-to-filament transition and flocculation. The N-terminal region (1-85) of CaCdc4 also has a positive role for its function, lost of which impairs both the ability to flocculate and to reverse filamentous growth in C. albicans.
CDC4 编码一种 F -box 蛋白，是 Skp1-Cdc53/Cul1-F-box (SCF) 泛素 E3 连接酶的成员，最初在芽殖酵母酿酒酵母中被鉴定为细胞周期 G1-S 转换过程中必需的基因。尽管白色念珠菌 CDC4（CaCDC4）可以释放酿酒酵母中缺失 CDC4 引起的有丝分裂缺陷，但 CaCDC4 是非必需的，并抑制丝状生长。
为了进一步阐明 CaCDC4 的功能，构建了一个缺失一个 CaCDC4 等位基因，另一个受可诱导表达的白色念珠菌 MET3 启动子（CaMET3p）调控的白色念珠菌菌株，然后引入能够在诱导表达不同白色念珠菌 Cdc4（CaCdc4）结构域的盒。在 Dox 诱导、但 CaMET3-CaCDC4 抑制条件下，各菌株的细胞均能表达特定的 CaCdc4 结构域。没有 F 盒或 WD40 重复结构域的细胞表现出与缺失 CaCDC4 表达相似的丝状生长和絮凝，表明 F 盒和 WD40 重复结构域的功能至关重要。值得注意的是，与表达全长 CaCdc4 的细胞相比，表达 N 端 85 个氨基酸截断的 CaCdc4 的细胞部分逆转了丝状生长，并削弱了絮凝能力，表明 CaCdc4 的 N 端 85 个氨基酸调节形态发生和絮凝。
CaCdc4 的 F 盒和 WD40 重复结构域对于抑制酵母向丝状过渡和絮凝是必需的。CaCdc4 的 N 端区域（1-85）对其功能也有积极作用，缺失会损害白色念珠菌的絮凝能力和丝状生长的逆转能力。
