RNase E, the major player in mRNA degradation, is down-regulated in Escherichia coli during a transient growth retardation (diauxic lag).
The endoribonuclease RNase E plays a major part in mRNA degradation in Escherichia coli in addition to its role in processing rRNA. RNase E is encoded by an essential gene, rne, also known as ams and hmp, which is autoregulated post-transcriptionally. Here we report a transient decrease in the steady state level of the full-length rne transcript and a corresponding decline in the amount of the protein and enzymatic activity. During this period an mRNA fragment, lacking an intact 5' end, accumulates. This down-regulation of RNase E occurs under aerobic growth conditions in rich medium during a short diauxic lag in mid-exponential phase; it most likely reflects an exhaustion of a not yet identified medium compound which is followed by switching on a new metabolic pathway. During this lag, the levels of bulk protein are maintained. Our results suggest that a transient drop in the intracellular RNase E level is a means of cells to retard mRNA turnover in a period of adjustment to medium utilization. Furthermore, the here described regulation of the rne transcript and its cognate gene product seems to occur by an RNase E-independent mechanism responsive to changes in growth conditions.
Barlow
T
T
Microbiology and Tumorbiology Center, Karolinska Institute, Stockholm, Sweden.
Berkmen
M
M
Georgellis
D
D
Bayr
L
L
Arvidson
S
S
von Gabain
A
A
D015536:Down-Regulation / Q000502:physiology; D004722:Endoribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000254:growth & development; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism*; D015183:Restriction Mapping
D012333:RNA, Messenger; D004722:Endoribonucleases; C022537:ribonuclease E