Repression of small toxic protein synthesis by the Sib and OhsC small RNAs.
The sequences encoding the QUAD1 RNAs were initially identified as four repeats in Escherichia coli. These repeats, herein renamed SIB, are conserved in closely related bacteria, although the number of repeats varies. All five Sib RNAs in E. coli MG1655 are expressed, and no phenotype was observed for a five-sib deletion strain. However, a phenotype reminiscent of plasmid addiction was observed for overexpression of the Sib RNAs, and further examination of the SIB repeat sequences revealed conserved open reading frames encoding highly hydrophobic 18- to 19-amino-acid proteins (Ibs) opposite each sib gene. The Ibs proteins were found to be toxic when overexpressed and this toxicity could be prevented by coexpression of the corresponding Sib RNA. Two other RNAs encoded divergently in the yfhL-acpS intergenic region were similarly found to encode a small hydrophobic protein (ShoB) and an antisense RNA regulator (OhsC). Overexpression of both IbsC and ShoB led to immediate changes in membrane potential suggesting both proteins affect the cell envelope. Whole genome expression analysis showed that overexpression of IbsC and ShoB, as well as the small hydrophobic LdrD and TisB proteins, has both overlapping and unique consequences for the cell.
Fozo
Elizabeth M
EM
Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, USA.
Kawano
Mitsuoki
M
Fontaine
Fanette
F
Kaya
Yusuf
Y
Mendieta
Kathy S
KS
Jones
Kristi L
KL
Ocampo
Alejandro
A
Rudd
Kenneth E
KE
Storz
Gisela
G
D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D016366:Open Reading Frames; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid; D016415:Sequence Alignment; D014169:Transformation, Bacterial
D012329:RNA, Bacterial