title: An internal antisense RNA regulates expression of the photosynthesis gene isiA.
abstract: 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.
authors.affiliation: Department of Plant Biochemistry, Institute of Biology, Humboldt-University Berlin, Chausseestrasse 117, D-10115 Berlin, Germany.
authors.forename: Ulf
authors.initials: U
authors.lastname: Dühring
authors.forename: Ilka M
authors.initials: IM
authors.lastname: Axmann
authors.forename: Wolfgang R
authors.initials: WR
authors.lastname: Hess
authors.forename: Annegret
authors.initials: A
authors.lastname: Wilde
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D007501:Iron / Q000378:metabolism*; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism; D009690:Nucleic Acid Conformation; D010788:Photosynthesis / Q000235:genetics* / Q000502:physiology; D016372:RNA, Antisense / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D016372:RNA, Antisense; C076726:chlorophyll A binding protein CP43, Cyanobacteria; D007501:Iron