Effects of DNA Methylation on Expression of Virulence Genes in Streptococcus mutans
Effects of DNA Methylation on Expression of Virulence Genes in Streptococcus mutans
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DOI：
10.1128/aem.00543-11
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发表时间：
2011-10-01
影响因子：
4.4
通讯作者：
Zhu, Min
中科院分区：
文献类型：
--
作者：
Banas, Jeffrey A.;Biswas, Saswati;Zhu, Min
细菌产生多种能够使DNA甲基化的酶。在许多物种中，大多数腺嘌呤甲基化是由DNA腺嘌呤甲基化酶Dam完成的。在大肠杆菌中，Dam甲基化酶在复制起始、错配修复和基因调控中起作用。在许多其他细菌物种中，Dam的突变或过表达导致毒力减弱。dam基因的同源物存在于厚壁菌门的一些成员中，包括变形链球菌（一种牙齿病原体）。色葡萄对dam基因（SMU.504;此处指定为damA）中失活的变异株进行工程改造，并检查与致龋性相关的表型。一个突出的观察结果是，damA突变体产生的葡聚糖量大于亲本菌株。实时PCR证实了gtfB的上调。为了确定其他基因座是否受到damA突变的影响，进行了微阵列分析。70个基因在damA突变体中上调至少2倍，33个基因下调至少2倍。除了gtfB（上调2.6倍;当通过实时PCR测量时为1.7倍）之外，其他上调的毒力因子包括gbpC（上调2.1倍）和预测编码细菌素的基因座（上调2至7倍）。各种糖转运操纵子也上调，最极端的是纤维二糖操纵子（上调近40倍）。编码果糖基转移酶的sacB的表达下调2.4倍。序列5 '-GATC-3'似乎构成甲基化的识别序列。这些结果为S.变形杆菌对基因表达具有全局影响，包括与致龋潜能相关的基因的表达。
Bacteria produce a variety of enzymes capable of methylating DNA. In many species, the majority of adenine methylation is accomplished by the DNA adenine methylase Dam. In Escherichia coli the Dam methylase plays roles in the initiation of replication, mismatch repair, and gene regulation. In a number of other bacterial species, mutation or overexpression of Dam leads to attenuation of virulence. Homologues of the dam gene exist in some members of the Firmicutes, including Streptococcus mutans, a dental pathogen. An S. mutans strain inactivated in the dam gene (SMU.504; here designated damA) was engineered, and phenotypes linked to cariogenicity were examined. A prominent observation was that the damA mutant produced greater amounts of glucan than the parental strain. Real-time PCR confirmed upregulation of gtfB. To determine whether other loci were affected by the damA mutation, a microarray analysis was carried out. Seventy genes were upregulated at least 2-fold in the damA mutant, and 33 genes were downregulated at least 2-fold. In addition to gtfB (upregulated 2.6-fold; 1.7-fold when measured by real-time PCR), other upregulated virulence factors included gbpC (upregulated 2.1-fold) and loci predicted to encode bacteriocins (upregulated 2- to 7-fold). Various sugar transport operons were also upregulated, the most extreme being the cellobiose operon (upregulated nearly 40-fold). Expression of sacB, encoding fructosyltransferase, was downregulated 2.4-fold. The sequence 5'-GATC-3' appeared to constitute the recognition sequence for methylation. These results provide evidence that DNA methylation in S. mutans has a global effect on gene expression, including that of genes associated with cariogenic potential.