IscR regulates RNase LS activity by repressing rnlA transcription.
The Escherichia coli endoribonuclease LS was originally identified as a potential antagonist of bacteriophage T4. When the T4 dmd gene is defective, RNase LS cleaves T4 mRNAs and antagonizes T4 reproduction. This RNase also plays an important role in RNA metabolisms in E. coli. rnlA is an essential gene for RNase LS activity, but the transcriptional regulation of this gene remains to be elucidated. An Fe-S cluster protein, IscR, acts as a transcription factor and controls the expression of genes that are necessary for Fe-S cluster biogenesis. Here, we report that overexpression of IscR suppressed RNase LS activity, causing the loss of antagonist activity against phage T4. This suppressive effect did not require the ligation of Fe-S cluster into IscR. beta-Galactosidase reporter assays showed that transcription from an rnlA promoter increased in iscR-deleted cells compared to wild-type cells, and gel-mobility shift assays revealed specific binding of IscR to the rnlA promoter region. RT-PCR analysis demonstrated that endogenous rnlA mRNA was reduced by overexpression of IscR and increased by deletion of iscR. From these results, we conclude that IscR negatively regulates transcription of rnlA and represses RNase LS activity.
Otsuka
Yuichi
Y
Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan.
Miki
Kumiko
K
Koga
Mitsunori
M
Katayama
Natsu
N
Morimoto
Wakako
W
Takahashi
Yasuhiro
Y
Yonesaki
Tetsuro
T
D015153:Blotting, Western; D024202:Electrophoretic Mobility Shift Assay; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D007506:Iron-Sulfur Proteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012260:Ribonucleases / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D024363:Transcription Initiation Site; D014158:Transcription, Genetic; D001616:beta-Galactosidase
D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins; C499695:IscR protein, E coli; D012333:RNA, Messenger; D012097:Repressor Proteins; C525943:RnlA protein, E coli; D014157:Transcription Factors; C525942:RNase LS, E coli; D012260:Ribonucleases; D001616:beta-Galactosidase