Article,
An internal antisense RNA regulates expression of the photosynthesis gene isiA
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 103 (18): 7054-7058 (2006)
Abstract
Small regulatory noncoding RNAs exist in both eukaryotic and
prokaryotic organisms. Most of these RNA transcripts are transencoded
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.
