CBB seminar Monday, June 19, 2:00 pm, Bldg. 38A, B2 library

Identification and functions of cis- and trans-encoded non-coding RNAs in cyanobacteria and plants

Wolfgang R. Hess,
Professor for Experimental Bioinformatics 
University Freiburg, Inst. Biology II, Freiburg, Germany
http://www.cyanolab.de/

Tentative abstract (from PNAS 103: 7054-7058):
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.
 
If you would like to meet Dr. Hess before or after the talk, please let me know.