Robledo Marta, Frage Benjamin, Wright Patrick R, Becker Anke
LOEWE Center for Synthetic Microbiology and Faculty of Biology, Philipps-University Marburg, Marburg, Germany.
Bioinformatics Group, Department of Computer Science, Albert-Ludwigs-University Freiburg, Freiburg, Germany.
PLoS Genet. 2015 Apr 29;11(4):e1005153. doi: 10.1371/journal.pgen.1005153. eCollection 2015 Apr.
Mechanisms adjusting replication initiation and cell cycle progression in response to environmental conditions are crucial for microbial survival. Functional characterization of the trans-encoded small non-coding RNA (trans-sRNA) EcpR1 in the plant-symbiotic alpha-proteobacterium Sinorhizobium meliloti revealed a role of this class of riboregulators in modulation of cell cycle regulation. EcpR1 is broadly conserved in at least five families of the Rhizobiales and is predicted to form a stable structure with two defined stem-loop domains. In S. meliloti, this trans-sRNA is encoded downstream of the divK-pleD operon. ecpR1 belongs to the stringent response regulon, and its expression was induced by various stress factors and in stationary phase. Induced EcpR1 overproduction led to cell elongation and increased DNA content, while deletion of ecpR1 resulted in reduced competitiveness. Computationally predicted EcpR1 targets were enriched with cell cycle-related mRNAs. Post-transcriptional repression of the cell cycle key regulatory genes gcrA and dnaA mediated by mRNA base-pairing with the strongly conserved loop 1 of EcpR1 was experimentally confirmed by two-plasmid differential gene expression assays and compensatory changes in sRNA and mRNA. Evidence is presented for EcpR1 promoting RNase E-dependent degradation of the dnaA mRNA. We propose that EcpR1 contributes to modulation of cell cycle regulation under detrimental conditions.
响应环境条件调节复制起始和细胞周期进程的机制对微生物存活至关重要。对植物共生α-变形菌苜蓿中华根瘤菌中转编码小非编码RNA（反式sRNA）EcpR1的功能表征揭示了这类核糖调节因子在调节细胞周期调控中的作用。EcpR1在根瘤菌目至少五个家族中广泛保守，预计会形成具有两个确定茎环结构域的稳定结构。在苜蓿中华根瘤菌中，这种反式sRNA编码在divK-pleD操纵子下游。ecpR1属于严谨反应调节子，其表达受多种应激因素诱导且在稳定期表达。诱导型EcpR1过量表达导致细胞伸长和DNA含量增加，而删除ecpR1则导致竞争力下降。通过计算预测的EcpR1靶标富含细胞周期相关mRNA。通过双质粒差异基因表达分析以及sRNA和mRNA中的补偿性变化，实验证实了由mRNA与EcpR1高度保守的环1碱基配对介导的细胞周期关键调节基因gcrA和dnaA的转录后抑制。有证据表明EcpR1促进了dnaA mRNA的核糖核酸酶E依赖性降解。我们提出EcpR1在有害条件下有助于调节细胞周期调控。
