This is paper n°6 in the series « Extrinsic Factors in Ribosome Assembly »; paper n°5 is El Hage and Alix (2004).
Ribosome biogenesis is temperature-dependent and delayed in Escherichia coli lacking the chaperones DnaK or DnaJ†
Article first published online: 1 DEC 2008
© 2008 The Authors. Journal compilation © 2008 Blackwell Publishing Ltd
Volume 71, Issue 3, pages 748–762, February 2009
How to Cite
Al Refaii, A. and Alix, J.-H. (2009), Ribosome biogenesis is temperature-dependent and delayed in Escherichia coli lacking the chaperones DnaK or DnaJ. Molecular Microbiology, 71: 748–762. doi: 10.1111/j.1365-2958.2008.06561.x
- Issue published online: 14 JAN 2009
- Article first published online: 1 DEC 2008
- Accepted 20 November, 2008.
In Escherichia coli strains carrying null mutations in either the dnaK or dnaJ genes, the late stages of 30S and 50S ribosomal subunit biogenesis are slowed down in a temperature-dependent manner. At high temperature (44°C), 32S and 45S particles (precursors to 50S subunits) and 21S particles (precursors to 30S subunits) accumulate. The latter are shown by 3′5′ rapid amplification of cDNA ends analysis to contain unprocessed or partially processed 16S ribosomal RNA at the 5′ end, but the 3′ end was never processed. This implies that maturation of 16S ribosomal RNA starts at the 5′-terminus, and that the 3′-terminus is only trimmed at a later step. At normal temperatures (30°C−37°C), ribosome assembly in both mutants is not arrested but is significantly delayed, as shown by pulse-chase analysis. Assembly defects are partially compensated by an overexpression of other heat-shock proteins, which occurs in the absence of their negative regulator DnaK, or by a plasmid-driven overexpression of GroES/GroEL, suggesting the involvement of a network of chaperones in ribosome biogenesis.