Protease‐deficient SOS constitutive cells have RecN‐dependent cell division phenotypes

Abstract

In Escherichia coli, after DNA damage, the SOS response increases the transcription (and protein levels) of approximately 50 genes. As DNA repair ensues, the level of transcription returns to homeostatic levels. ClpXP and other proteases return the high levels of several SOS proteins to homeostasis. When all SOS genes are constitutively expressed and many SOS proteins are stabilized by the removal of ClpXP, microscopic analysis shows that cells filament, produce mini-cells and have branching protrusions along their length. The only SOS gene required (of 19 tested) for the cell length phenotype is recN. ClpXP or recN4174 (A552S, A553V), a mutant not recognized by ClpXP, produce filamentous cells with nucleoid partitioning defects. It is hypothesized that when produced at high levels during the SOS response, RecN interferes with nucleoid partitioning and Z-Ring function by holding together sections of the nucleoid, or sister nucleoids, providing another way to inhibit cell division. RecN is a member of the Structural Maintenance of Chromosome (SMC) class of proteins. It can hold pieces of DNA together and is important for doublestrand break repair (DSBR). RecN is degraded by ClpXP. Overexpression of recN + in the absence of

Topological DNA-binding of structural maintenance of chromosomes-like RecN promotes DNA double-strand break repair in Escherichia coli

“…In this regard, it is interesting to note that E. coli RecN is rapidly degraded by the ClpXP protease in a manner dependent upon the signaling residues at the C terminus of RecN, which are not conserved among other RecN orthologs 48,49 . Efficient removal of topologically associated RecN and DNA may be essential for the growth recovery process, as these structures could interfere with chromosome segregation and lead to genetic instability 50 . Hence, we speculate that a ClpXP-dependent mechanism may play a role in removing some amount of RecN remaining on the DNA during growth recovery.…”

Ultrasonic cavitation induced Vibrio parahaemolyticus entering an apoptosis-like death process through SOS response

“…Meanwhile, the induction of the SOS response in cells due to external stress processes also triggered the expression of RecN proteins to coordinate double-strand break repair. During homologous recombination of double-strand breaks, RecN might interact with RecA to facilitate homology search and strand invasion [40] .…”

Mutational Analysis of Residues in PriA and PriC Affecting Their Ability To Interact with SSB in Escherichia coli K-12

“…To overproduce SSB, we introduced a strong constitutive promoter and an improved ribosome binding site (RBS) upstream of the ssb gene as previously described for radA and recN (45,46). Briefly, the strong promoter and optimized RBS were linked to a flippable chloramphenicol resistance gene and inserted just upstream of the ssb gene (see Materials and Methods).…”