Initiation of DNA replication in Δcya mutants of Escherichia coli K12

Landoulsi, Ameni

doi:10.1016/s0300-9084(00)87166-7

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“…In E. coli , ppGpp negatively regulates dnaA , which encodes DnaA, the replication initiator protein, and cAMP binds DnaA, in a complex interplay through which DNA synthesis is inhibited (Cashel et al, 1996; Landoulsi and Kohiyama, 1999; Chatterji and Ojha, 2001). Furthermore, replication elongation is stalled shortly after amino acid starvation-induced ppGpp expression in Bacillus subtilis (Wang et al, 2007).…”

Section: Resultsmentioning

confidence: 99%

Global Regulators Orchestrate Group II Intron Retromobility

et al. 2009

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SUMMARY Group II introns are hypothesized to share common ancestry with both nuclear spliceosomal introns and retrotransposons, which collectively occupy the majority of genome space in higher eukaryotes. These phylogenetically diverse introns are mobile retroelements that move through an RNA intermediate. Disruption of Escherichia coli genes encoding enzymes that catalyze synthesis of global regulators cAMP and ppGpp inhibits group II intron retromobility. These small molecules program genetic transitions between nutrient excess and starvation. Accordingly, we demonstrated that glucose depletion of wild-type cells and cAMP supplementation of mutants stimulated retromobility. Likewise, amino acid starvation, which induces the alarmone ppGpp, activated retromobility. In both cases, retrotransposition to ectopic sites was favored over retrohoming. Interestingly, these stimulatory effects are mediated at the level of the DNA target, rather than of expression of the retroelement. Thereby, during metabolic stress, cAMP and ppGpp control group II intron movement in concert with the cell’s global genetic circuitry, stimulating genetic diversity.

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Section: Resultsmentioning

confidence: 99%