Suppression of a cold-sensitive mutation in ribosomal protein S5 reveals a role for RimJ in ribosome biogenesis

A specific mutation of Escherichia coli ribosomal protein S5, in which glycine is changed to aspartate at position 28 [S5(G28D)], results in cold sensitivity and defects in ribosome biogenesis and translational fidelity. In an attempt to understand the roles of S5 in these essential cellular functions, we selected extragenic suppressors and identified rimJ as a high-copy suppressor of the cold-sensitive phenotype associated with the S5(G28D) mutation. Our studies indicate that RimJ overexpression suppresses the growth defects, anomalous ribosome profiles and mRNA misreading exhibited by the S5(G28D) mutant strain. Although previously characterized as the N-acetyltransferase of S5, our data indicate that RimJ, when devoid of acetyltransferase activity, can suppress S5(G28D) defects thus indicating that the suppression activity of RimJ is not dependent on its acetyltransferase activity. Additionally, RimJ appears to associate with pre-30S subunits indicating that it acts on the ribonucleoprotein particle. These findings suggest that RimJ has evolved dual functionality; it functions in r-protein acetylation and as a ribosome assembly factor in E. coli

Take a chance on Science:: Experiments in Science learning

Most of us chose a career in science because the natural world tickled our intellect, and our curiosity beckoned. Yet in the classroom, science is often presented as a static collection of facts rather than a vibrant method of inquiry that ignites curiosity and fuels discovery. What can we do about that? I chose to celebrate science by embracing its philosophy and practices in the classroom. I use my intuition about what will work, make hypotheses, try things out and experiment, sometimes fail and sometimes succeed, and use that data to readjust my hypothesis. And every day, I repeat the mantra that science education is not about coming up with the right answer; it’s about learning to ask insightful questions. In this session, I will take you through my experiments in science education, first using the case study discussion technique to encourage students to think like a scientist. Then I’ll share the lessons learned by leaving academia and continuing a career in informal education at a science centre. Along the way, I will offer opportunities to reflect on your practice, how you model the scientific process in your classroom to feed students’ inquisitiveness, and your approach to taking risks in the classroom

DEAD-box RNA helicases in gram-positive RNA decay

DEAD-box RNA helicases are important players in eukaryotic and bacterial RNA metabolism. A helicase from Staphylococcus aureus was recently shown to affect RNA decay, most likely via its interaction with the proposed Gram-positive degradosome. Some, but not all, RNAs are stabilized when the helicase CshA is mutated, and among the affected RNAs is the agrBDCA mRNA, which is responsible for quorum sensing in S. aureus. We describe how the stabilization of agr mRNA (and others) can be measured and how to conduct assays to measure the effects of quorum-sensing defects, such as biofilm formation and hemolysin production

DEAD-Box Proteins from Escherichia coli Exhibit Multiple ATP-Independent Activities▿

DEAD-box proteins (DBPs) are a widespread class of ATP-dependent RNA helicases that play a key role in unwinding RNA duplexes. In recent years, certain DBPs have also been found to exhibit activities that do not require ATP. To gain a better understanding of prokaryotic RNA metabolism, we investigated whether Escherichia coli DBPs harbor any ATP-independent activities. We show that each of the four E. coli DBPs tested in this study can accelerate the association of cRNA molecules, can stimulate strand displacement, and can function as an RNA chaperone without utilizing ATP. To the best of our knowledge, these prokaryotic DBPs constitute the first examples of proteins that harbor each of these three activities. The identification of these auxiliary functions indicates that the E. coli DBPs are versatile factors that possess significant RNA remodeling activity in addition to their canonical RNA helicase activity and might therefore participate in a greater variety of cellular processes than has been previously appreciated