antitermination
Processive
antitermination occurs when bacterial RNA polymerase becomes
allosterically altered by accessory factors, such as elongation factors,
to become resistant to downstream pausing and termination signals. The
most thoroughly analyzed examples affect transcription of the lambda
phage genome and rRNA genes in E. coli.
However, such mechanisms have been less characterized in
non-proteobacterial species. Indeed, only five classes have been
described overall and more than a decade has passed since the last new
example. We have discovered a novel processive antitermination mechanism
that is required for synthesis of biofilm and capsular polysaccharide
genes. This particular antitermination mechanism is mediated by an RNA
element that is conserved among Bacillales. These observations suggest
that processive antitermination may be mediated by structurally complex
noncoding RNAs and may be widespread in Gram-positive bacteria as a
mechanism to ensure full synthesis of particular classes of operons.
Given the increasing pace that noncoding and regulatory RNAs are being
identified, this discovery suggests that there could be other
uncharacterized RNA elements that play a role in processive
antitermination.