Biology subjects

Chmbers, L. R.

Publications and source records attributed to Chmbers, L. R..

3 recordsLinked to original sources

bioRxiv2026

A RecBCD-like enzyme regulates expression of bacterial defense operons in response to DNA damage

Bacteria must quickly respond to stress signals including bacteriophage (phage) infection, invasion by mobile genetic elements, and other threats. DNA damage is a stress-signaling nexus in bacteria, initiating global responses such as the SOS response and triggering expression of specific defense and immune pathways through DNA damage-sensing transcriptional regulators. Here we identify a three-protein pathway termed Cerberus that senses dsDNA ends that become available during DNA damage or inhibition of the key DNA repair complex RecBCD, and controls expression of an associated defense/immune operon. The central player in Cerberus is a large peptidase-helicase-nuclease fusion protein, CerC, that is architecturally similar to the RecBC complex itself. Upon DNA damage or RecBCD inhibition, CerC binds and unwinds free DNA ends to allosterically activate its fused HExxH metallopeptidase domain. CerC specifically cleaves the adjacently encoded anti-sigma factor CerB to release its cognate sigma factor CerA, allowing CerA to mediate transcription of a defense/immune operon encoded nearby. Cerberus therefore represents a pathway that has co-opted a key DNA repair machine for DNA damage sensing, and linked that activity to transcriptional control through anti-sigma factor cleavage.

biochemistry↗

bioRxiv2026

Molecular mechanism of a single stranded DNA-stimulated bacterial immune peptidase

Bacteria encode hundreds of immune pathways that protect host cells against infection by bacteriophages. While immune pathways possess exquisite mechanisms for self-regulation to avoid aberrant activation, many are also tightly regulated at the level of transcription. Many immune operons are regulated by CapP+CapH, a two-protein transcriptional regulator system that triggers immune operon expression in response to DNA damage, by sensing the presence of single-stranded DNA byproducts of DNA damage repair. Here we define how the CapP peptidase is activated by single-stranded DNA. DNA binding in a conserved inter-domain groove in CapP triggers rearrangement of the autoregulatory "cysteine switch loop", opening the active site and allowing binding and cleavage of CapH, which in turn leads to transcriptional activation of an associated immune operon. Our data define a conserved molecular mechanism for sensing bacteriophage infection via DNA damage, and for triggering increased expression of immune operons in response.

biochemistry↗

bioRxiv2026

A DNA damage-activated kinase controls bacterial immune pathway expression

Bacteria encode myriad stress-response pathways that protect their hosts against both internal and external threats. A key question is how these pathways are regulated, especially anti-phage immune pathways that mediate host cell killing. Here, we identify two proteins termed CapK and CapS that are encoded upstream of diverse immune operons, and regulate their expression in response to DNA damage. CapK resembles bacterial anti-sigma factor kinases, and CapS resembles these proteins STAS domain antagonists. CapS is a DNA-binding transcriptional repressor, and phosphorylation of CapS by CapK results in dissociation of a CapS homodimer and de-repression of transcription. CapKs kinase activity is directly activated by single-stranded DNA generated as a by-product of DNA repair. Finally, we show that CapK and CapS-like proteins have been co-opted into an anti-phage toxin-antitoxin system with a VapC-like protein, where they similarly respond to DNA damage to activate VapCs nuclease activity. Overall, our results reveal how a kinase-substrate pair can regulate expression of an adjacent operon in response to DNA damage, and highlight the modularity of immune and other stress-response pathways.

microbiology↗