Transcriptional Switch On of ssgA by A-Factor, Which Is Essential for Spore Septum Formation in Streptomyces griseus
Transcriptional Switch On of ssgA by A-Factor, Which Is Essential for Spore Septum Formation in Streptomyces griseus
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DOI：
10.1128/jb.185.4.1273-1283.2003
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发表时间：
2003-02
影响因子：
3.2
通讯作者：
H. Yamazaki;Y. Ohnishi;S. Horinouchi
中科院分区：
文献类型：
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作者：
H. Yamazaki;Y. Ohnishi;S. Horinouchi
摘要A因子(2-isocapryloyl-3R-hydroxymethyl-γ-butyrolactone)触发灰色链霉菌的形态发育和次生代谢。A因子调控级联中的转录激活因子(AdpA)启动了两个过程所需的一些基因。AdBS11是从AdpA结合的DNA片段文库中鉴定出来的，并定位在SSgA的上游，SSgA是气生菌丝形成隔膜所必需的。凝胶迁移率改变分析和DNA酶I足迹分析显示，与−转录起点p1相比，在SSgA235(第1位)、−110(第2位)和+60(第3位)的核苷酸位置有3个AdpA结合位点。SSgA有两个转录起始点，一个起始于SSgA起始密码子上游的124个核苷酸(P1)，另一个起始于79个核苷酸(P2)。在这三个结合位点中，只有1和2位点是AdpA转录激活p1和p2所必需的。SSgA的转录启动除了需要σ外，还需要胞外功能的Sigma因子AdsA。然而，σadsa不太可能识别这两个SSgA启动子，因为它们的−35和−10序列与天蓝色链霉菌A3(2)的σadsa同源物σBldN识别的启动子序列不相似。SSgA干扰物形成气生菌丝，但不形成孢子，这表明SSgA是WHI基因的成员。对SSfR的转录分析表明，没有从SSfR读入SSgA，SSgA在没有SSfR的情况下转录。因此，发现SSgA在可检测的范围内受AdpA控制，而不受SsfR控制。SsfR似乎独立于SSgA或通过某种未知的方式与SSgA相互作用来调节孢子隔膜的形成，因为一种SSfR干扰物也表现出Whi表型。
ABSTRACT A-factor (2-isocapryloyl-3R-hydroxymethyl-γ-butyrolactone) triggers morphological development and secondary metabolism in Streptomyces griseus. A transcriptional activator (AdpA) in the A-factor regulatory cascade switches on a number of genes required for both processes. AdBS11 was identified in a library of the DNA fragments that are bound by AdpA and mapped upstream of ssgA, which is essential for septum formation in aerial hyphae. Gel mobility shift assays and DNase I footprinting revealed three AdpA-binding sites at nucleotide positions about −235 (site 1), −110 (site 2), and +60 (site 3) with respect to the transcriptional start point, p1, of ssgA. ssgA had two transcriptional start points, one starting at 124 nucleotides (p1) and the other starting at 79 nucleotides (p2) upstream of the start codon of ssgA. Of the three binding sites, only sites 1 and 2 were required for transcriptional activation of p1 and p2 by AdpA. The transcriptional switch on of ssgA required the extracytoplasmic function sigma factor, σAdsA, in addition to AdpA. However, it was unlikely that σAdsA recognized the two ssgA promoters, since their −35 and −10 sequences were not similar to the promoter sequence motifs recognized by σBldN, a σAdsA homologue of Streptomyces coelicolor A3(2). An ssgA disruptant formed aerial hyphae, but did not form spores, irrespective of the carbon source of the medium, which indicated that ssgA is a member of the whi genes. Transcriptional analysis of ssfR, located just upstream of ssgA and encoding an IclR-type transcriptional regulator, suggested that no read-through from ssfR into ssgA occurred, and ssgA was transcribed in the absence of ssfR. ssgA was thus found to be controlled by AdpA and not by SsfR to a detectable extent. SsfR appeared to regulate spore septum formation independently of SsgA or through interaction with SsgA in some unknown way, because an ssfR disruptant also showed a whi phenotype.