Two modes of control of pilA, the gene encoding type 1 pilin in Escherichia coli.
Two modes of control of pilA, the gene encoding type 1 pilin in Escherichia coli.
复制标题
pilA（大肠杆菌中编码 1 型菌毛蛋白的基因）的两种控制模式。
DOI：
10.1128/jb.164.1.321-330.1985
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发表时间：
1985
影响因子：
3.2
通讯作者：
Falkow,S
中科院分区：
文献类型：
--
作者：
Orndorff,PE;Spears,PA;Schauer,D;Falkow,S
大肠杆菌中的1型亲和在转录水平上受亚稳态调控（b.i. Eisenstein, Science 214:337-339, 1981）。然而，控制这种方式的基因尚不清楚。我们提出的证据表明，编码1型毛的结构亚基的毛a基因受亚稳态转录调控。在重组质粒上构建了pilA'-lacZ融合体，并与大肠杆菌K-12的recBC sbcB突变体结合，将融合体引入编码Pil的染色体区域。这种融合被发现受亚稳态转录控制。从Lac+表型到Lac-表型的转换速率为每代每个细胞4 × 10(-4)，相反方向为6.2 × 10（-4）。在表型“ON”（Lac+）和“OFF”（Lac-）群体之间观察到β -半乳糖苷酶活性约10倍的差异。P1转导实验表明，决定ON或OFF表型的元件与pilA紧密相连。除了pilA的亚稳态调控外，第二种类型的转录调控是由邻近pilA的基因产物hyp影响的。通过使用只包含pilA'-lacZ融合和假定的pilA启动子的重组质粒，我们发现hyp损伤的β -半乳糖苷酶活性比具有亲本hyp基因的菌株高约5倍。构建具有pilA'- lacz融合和染色体上hyp::Tn5-132突变的突变体显示出从Lac+切换到Lac-的频率，反之亦然，与亲本菌株没有区别。然而，在ON模式下，hyp::Tn5-132突变体表现出两倍高的β -半乳糖苷酶活性。因此，hyp似乎不影响亚稳态变异，但确实影响ON（转录）模式下pilA基因的转录水平。
Type 1 piliation in Escherichia coli is subject to metastable regulation at the transcriptional level (B. I. Eisenstein, Science 214:337-339, 1981). However, the genes controlling in this fashion are not known. We present evidence that the pilA gene, encoding the structural subunit of type 1 pili, is subject to metastable transcriptional regulation. A pilA'-lacZ fusion, constructed in vitro on a recombinant plasmid, was used in conjunction with a recBC sbcB mutant of E. coli K-12 to introduce the fusion into the chromosomal region encoding Pil. This fusion was found to be subject to metastable transcriptional control. The rate of switching from the Lac+ to the Lac- phenotype was 4 X 10(-4) per cell per generation and 6.2 X 10(-4) in the opposite direction. A ca. 10-fold difference in beta-galactosidase activity was observed between phenotypically "ON" (Lac+) and "OFF" (Lac-) populations. P1 transduction experiments showed that the element determining the ON or OFF phenotype was tightly linked to pilA. In addition to the metastable regulation of pilA, a second type of transcriptional regulation was effected by the product of a gene, hyp, adjacent to pilA. By using a recombinant plasmid containing just a pilA'-lacZ fusion and the putative pilA promoter, we found that a lesion in hyp conferred a beta-galactosidase activity about fivefold higher than that of a strain possessing the parental hyp gene. Mutants constructed to have a pilA'-lacZ fusion and a hyp::Tn5-132 mutation in the chromosome exhibited a frequency of switching from Lac+ to Lac- and vice versa indistinguishable from that of the parental strain. However, in the ON mode, hyp::Tn5-132 mutants showed a twofold-higher beta-galactosidase activity. Thus, hyp does not appear to affect metastable variation but does affect the level of transcription of the pilA gene in the ON (transcribed) mode.