Second messenger-mediated spatiotemporal control of protein degradation regulates bacterial cell cycle progression

Abstract

Second messengers control a wide range of important cellular functions in eukaryotes and prokaryotes. Here we show that cyclic di-GMP, a global bacterial second messenger, promotes cell cycle progression in Caulobacter crescentus by mediating the specific degradation of the replication initiation inhibitor CtrA. During the G1-to-Sphase transition, both CtrA and its cognate protease ClpXP dynamically localize to the old cell pole, where CtrA is rapidly degraded. Sequestration of CtrA to the cell pole depends on PopA, a newly identified cyclic di-GMP effector protein. PopA itself localizes to the cell pole and directs CtrA to this subcellular site via the direct interaction with a mediator protein, RcdA. We present evidence that c-di-GMP regulates CtrA degradation during the cell cycle by controlling the dynamic sequestration of the PopA recruitment factor to the cell pole. Furthermore, we show that cell cycle timing of CtrA degradation relies on converging pathways responsible for substrate and protease localization to the old cell pole. This is the first report that links cyclic di-GMP to protein dynamics and cell cycle control in bacteria.[Keywords: PopA; cyclic di-GMP; protein degradation; Caulobacter crescentus; cell cycle; second messenger] Supplemental material is available at http://www.genesdev.org.

The c-di-GMP recognition mechanism of the PilZ domain of bacterial cellulose synthase subunit A

“…Cyclic dimeric guanosine monophosphate (c-di-GMP) is a bacterial second messenger that controls a wide variety of cellular processes, such as biofilm formation [1], virulence [2], cell cycle [3], and motility [3,4]. In the c-di-GMP-dependent signaling cascades, c-di-GMP binds to different effectors, including transcription factors, degenerate GGDEF/EAL domain-containing proteins, PilZ domain-containing proteins, and even nucleotides; riboswitches [5,6].…”

“…Another transcription factor, Clp, from the plant pathogen Xanthomonas campestris suppresses virulence gene expression by increased intracellular level of c-di-GMP coupled with a quorum sensing system [2]. In Caulobacter crescentus, PopA that has a degenerate GGDEF motif binds c-di-GMP and is localized around the cell pole to interact with the downstream components for controlling the cell cycle [3]. DgrA from C. crescentus, which is classified as a PilZ domain-containing protein, blocks cell motility linked to flagellar motor function upon c-di-GMP binding [4].…”

Electron-shuttling antibiotics structure bacterial communities by modulating cellular levels of c-di-GMP

“…4A). I-sites can participate in noncompetitive allosteric inhibition, and can be found in noncatalytic c-di-GMP binding proteins (35) but are often found in proteins with DGC activity (20). Indeed, we note that properties of rmcA+ AAA colonies, constitutively overexpressing a version of RmcA with an intact GGDEF motif and no EAL motif, are consistent with a DGC activity for this protein, as they exhibit: (i) a distinct phenotype, with taller structures forming emanating spokes, and (ii) higher c-di-GMP and matrix levels, relative to colonies of ΔrmcA (Fig.…”

Structural basis of differential ligand recognition by two classes of bis-(3′-5′)-cyclic dimeric guanosine monophosphate-binding riboswitches

“…The affinity of these RNAs for their ligand is very high; class I riboswitches have a K d as tight as 10 pM (23) (1,2,(9)(10)(11)(12)(13)(14)(15)(16). Whereas a few bacteria contain examples of both classes, several species lacking a class I riboswitch use c-di-GMP for signaling and have exclusively a class II riboswitch (19).…”

“…To alter gene expression or protein activity in response to external or internal signals, c-di-GMP interacts with several proteins (1,2,(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). In addition, two classes of RNAs have been reported that bind this second messenger, the c-di-GMP-I (class I) and c-di-GMP-II (class II) riboswitches (18,19).…”