A transcriptional regulator, IscR, of Burkholderia multivorans acts as both repressor and activator for transcription of iron-sulfur cluster-biosynthetic isc operon

Fe-S cluster homeostasis and beyond: The multifaceted roles of IscR

The role of IscR in regulating the transcription of genes involved in Fe-S cluster homeostasis has been well established for the model organism Escherichia coli K12. In this bacterium, IscR coordinates expression of the Isc and Suf Fe-S cluster assembly pathways to meet cellular Fe-S cluster demands shaped by a variety of environmental cues. However, since its initial discovery nearly 25 years ago, there has been growing evidence that IscR function extends well beyond Fe-S cluster homeostasis, not only in E. coli, but in bacteria of diverse lifestyles. Notably, pathogenic bacteria have exploited the ability of IscR to respond to changes in oxygen tension, oxidative and nitrosative stress, and iron availability to navigate their trajectory in their respective hosts as changes in these cues are frequently encountered during host infection. In this review, we highlight these broader roles of IscR in different cellular processes and, in particular, discuss the importance of IscR as a virulence factor for many bacterial pathogens.

Genetic dissection of the bacterial Fe-S protein biogenesis machineries

Iron‑sulfur (Fe-S) clusters are one of the most ancient and versatile inorganic cofactors present in the three domains of life. Fe-S clusters are essential cofactors for the activity of a large variety of metalloproteins that play crucial physiological roles. Fe-S protein biogenesis is a complex process that starts with the acquisition of the elements (iron and sulfur atoms) and their assembly into an Fe-S cluster that is subsequently inserted into the target proteins. The Fe-S protein biogenesis is ensured by multiproteic systems conserved across all domains of life. Here, we provide an overview on how bacterial genetics approaches have permitted to reveal and dissect the Fe-S protein biogenesis process in vivo.

Clamping-mediated incorporation of single-stranded DNA with concomitant DNA synthesis by Taq polymerase involves nick-translation

The development and characterization of a new enzyme reaction contribute to advancements in modern biotechnology. Here, we report a novel CIS (clamping-mediated incorporation of single-stranded DNA with concomitant DNA synthesis) reaction catalyzed by Taq polymerase. In the reaction, a single-stranded DNA (ssDNA) with 3' Cs is attached with a preformed 3' G-tail of double-stranded DNA (dsDNA); DNA syntheses starting from both 3' ends result in the incorporation of ssDNA. A 3' G-tail length of 3 nucleotides adequately supports this reaction, indicating that Taq polymerase can clump short Watson-Crick base pairs as short as three pairs and use them to initiate DNA polymerization. The reverse transcriptase from Molony murine leukemia virus catalyzes strand displacement synthesis and produces flapped-end DNA, whereas the reaction by Taq polymerase involves the nick translation. These new reaction properties may be beneficial for the development of new molecular tools applicable in various fields. Apart from its CIS reaction activity, we also report that Taq polymerase has the undesirable characteristic of removing 5' fluorescent labels from dsDNA. This characteristic may have compromised various experiments involving the preparation of fluorescently-labeled dsDNA by PCR for a long time.