Dühring Ulf, Axmann Ilka M, Hess Wolfgang R, Wilde Annegret
Department of Plant Biochemistry, Institute of Biology, Humboldt-University Berlin, Chausseestrasse 117, D-10115 Berlin, Germany.
Proc Natl Acad Sci U S A. 2006 May 2;103(18):7054-8. doi: 10.1073/pnas.0600927103. Epub 2006 Apr 24.
Small regulatory noncoding RNAs exist in both eukaryotic and prokaryotic organisms. Most of these RNA transcripts are trans-encoded RNAs with short and only partial antisense complementarity to their target RNAs, which regulate gene expression by modifying mRNA stability and translation. In contrast, reports on the function of cis-encoded, perfectly complementary antisense RNAs in eubacteria are rare. Cyanobacteria respond to iron deficiency by expressing IsiA (iron stress-induced protein A), which forms a giant ring structure around photosystem I. Here, we show that this process is controlled by IsrR (iron stress-repressed RNA), a cis-encoded antisense RNA transcribed from the isiA noncoding strand. Artificial overexpression of IsrR under iron stress causes a strongly diminished number of IsiA-photosystem I supercomplexes, whereas IsrR depletion results in premature expression of IsiA. The coupled degradation of IsrR/isiA mRNA duplexes appears to be a reversible switch that can respond to environmental changes. IsrR is the only RNA known so far to regulate a photosynthesis component.
小型调控非编码RNA存在于真核生物和原核生物中。这些RNA转录本大多是反式编码的RNA，与它们的靶RNA具有短且仅部分反义互补性，通过改变mRNA稳定性和翻译来调控基因表达。相比之下，关于真细菌中顺式编码的、完全互补的反义RNA功能的报道很少。蓝细菌通过表达IsiA（铁应激诱导蛋白A）来应对缺铁，IsiA在光系统I周围形成一个巨大的环状结构。在这里，我们表明这个过程受IsrR（铁应激抑制RNA）控制，IsrR是一种从isiA非编码链转录而来的顺式编码反义RNA。在铁应激下人工过表达IsrR会导致IsiA-光系统I超复合物的数量大幅减少，而IsrR缺失则会导致IsiA过早表达。IsrR/isiA mRNA双链体的偶联降解似乎是一个可逆开关，能够响应环境变化。IsrR是迄今为止已知的唯一调控光合作用组分的RNA。
