Álvarez-Escribano Isidro, Brenes-Álvarez Manuel, Olmedo-Verd Elvira, Vioque Agustín, Muro-Pastor Alicia M
Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, 41092 Sevilla, Spain.
Life (Basel). 2020 Apr 29;10(5):54. doi: 10.3390/life10050054.
Small regulatory RNAs (sRNAs) are post-transcriptional regulators of bacterial gene expression. In cyanobacteria, the responses to nitrogen availability, that are mostly controlled at the transcriptional level by NtcA, involve also at least two small RNAs, namely NsiR4 (nitrogen stress-induced RNA 4) and NsrR1 (nitrogen stress-repressed RNA 1). Prediction of possible mRNA targets regulated by NsrR1 in sp. PCC 7120 allowed, in addition to previously described , the identification of , a nitrogen-regulated gene encoding a protein of unknown function that we describe here as required for growth at the expense of atmospheric nitrogen (N). We show that transcription of is induced upon nitrogen step-down independently of NtcA. All1871 accumulation is repressed by NsrR1 and its expression is stronger in heterocysts, specialized cells devoted to N fixation. We demonstrate specific interaction between NsrR1 and the 5' untranslated region (UTR) of the mRNA, that leads to decreased expression of . Because transcription of NsrR1 is partially repressed by NtcA, post-transcriptional regulation by NsrR1 would constitute an indirect way of NtcA-mediated regulation of .
小调控RNA（sRNA）是细菌基因表达的转录后调节因子。在蓝细菌中，对氮可用性的反应主要由NtcA在转录水平上控制，这也至少涉及两种小RNA，即NsiR4（氮胁迫诱导RNA 4）和NsrR1（氮胁迫抑制RNA 1）。对集胞藻PCC 7120中受NsrR1调控的可能mRNA靶标的预测，除了先前描述的之外，还鉴定出了一个氮调节基因，该基因编码一种功能未知的蛋白质，我们在此将其描述为以大气氮（N）为代价生长所必需的。我们表明，在氮含量下降时，All1871的转录独立于NtcA被诱导。All1871的积累受到NsrR1的抑制，并且其在异形胞（专门用于固氮的细胞）中的表达更强。我们证明了NsrR1与All1871 mRNA的5'非翻译区（UTR）之间存在特异性相互作用，这导致All1871的表达降低。由于NsrR1的转录部分受到NtcA的抑制，NsrR1的转录后调节将构成NtcA介导的All1871调节的间接方式。
