**6. Acknowledgements**

The work on *H. pylori* DNA repair in our laboratory was supported by NIH grant R21AI076569 and by the University of Georgia Foundation.

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DNA Repair Systems in *Helicobacter pylori* Diversity/Persistence 15

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modification diversity prevents genome subversion by chromosomal DNA from


(a) HP# refers to the gene number in the genome sequence of strain 26695 [12].

(b) DSB (double strand breaks) damage refers to those damages caused e.g. by ionizing radiation, mitomycin C, or ciprofloxacin.

Table 1. *H. pylori* genes involved in DNA recombinational repair

#### **7. References**


Gene HP # (a) Activity / function Main phenotypes of mutant (b) reference

[69, 92] addB 1089

[68, 71] recO 0951

recG 1523 Holiday junction helicase. Not sensitive to DNA damaging agents;

(b) DSB (double strand breaks) damage refers to those damages caused e.g. by ionizing radiation,

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ruvB 1059 Holiday junction helicase. Sensitive to DNA damaging agents;

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Sensitive to DSB damage; Sensitive to oxidative stress; Attenuated mouse colonization.

Not sensitive to DSB damage; Sensitive to oxidative stress; Attenuated mouse colonization.

Sensitive to DNA damaging agents; Decreased recombination frequency; Defective mouse colonization.

Sensitive to DNA damaging agents; Decreased recombination frequency; Attenuated mouse colonization.

Increased recombination frequency. [76]

Decreased recombination frequency. [75]

[83]

[65, 66, 69]

[73]

recN 1393 Initiates DSB-induced

recA 0153

addA 1553 AddAB Helicase-nuclease;

recR 0925 RecRO recombination pathway;

recombination.

Initiates DSB-induced recombination.

DNA recombinase; Catalyzes DNA pairing and

strand exchange.

ruvC 0877 Holliday junction resolvase.

mitomycin C, or ciprofloxacin.

**7. References** 

86.

Initiates ssDNA gap repair.

recJ 0348 5'-3' ssDNA exonuclease. Not studied experimently.

ruvA 0883 Holliday junction recognition. Not studied experimently.

(a) HP# refers to the gene number in the genome sequence of strain 26695 [12].

Table 1. *H. pylori* genes involved in DNA recombinational repair

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**1. Introduction** 

**enzymes** 

Michal Chai-Danino and Alexander Kotlyar

*Tel Aviv University, Israel* 

 \*

**2** 

**RloC: A Translation-Disabling tRNase Implicated in Phage Exclusion During** 

Bacteria respond to DNA damage by inducing the expression of numerous proteins involved in DNA repair and the reversible arrests of DNA replication and the cell division cycle (Fernandez De Henestrosa *et al*, 2000). This general rule may be violated by a conserved bacterial protein termed RloC (Davidov & Kaufmann, 2008). RloC combines structural-functional properties of two unrelated proteins (i) the universal DNA-damageresponsive/DNA-repair protein Rad50/SbcC (Williams *et al*, 2007) and (ii) the translationdisabling, phage-excluding anticodon nuclease (ACNase) PrrC (Blanga-Kanfi *et al*, 2006). These seemingly conflicting features may be reconciled in a model where RloC is mobilized as an antiviral back-up function during recovery from DNA damage (Davidov & Kaufmann, 2008), when DNA restriction, the cell's primary immune system is temporarily shut-off (Thoms & Wackernagel, 1984). Another intriguing feature of RloC is its ability to excise its substrate's wobble nucleotide (Davidov & Kaufmann, 2008). This harsh lesion is expected to encumber reversal by phage enzymes that repair the tRNA nicked by PrrC (Amitsur *et al*, 1987). Evaluating RloC's salient features and purported role requires prior description of its more familiar distant homolog PrrC and a DNA-damage-sensing device RloC shares with Rad50/SbcC. We conclude with an account of cellular RNA and DNA repair tools related to the phage tRNA repair mechanism that counteracts PrrC and may be frustrated by RloC.

**2. PrrC – A potential phage-excluding tool counteracted by tRNA repair** 

RNA repair may seem unnecessary because damaged RNA molecules can be readily replenished by re-synthesis. Yet, there exist situations where RNA repair could be the preferred or only possible option. A case in point is presented by an RNA repair pathway triggered by the ACNase PrrC. This conserved bacterial protein was detected in quest of roles of two phage T4-encoded enzymes: 3'-phosphatase/5'-polynucleotide kinase (PseT/Pnk,

Elena Davidov, Emmanuelle Steinfels-Kohn, Ekaterina Krutkina, Daniel Klaiman, Tamar Margalit,

**2.1 A host-phage survival cascade yields an RNA repair pathway** 

**Recovery from DNA Damage** 

Gabriel Kaufmann et al.\*

*Tel Aviv University* 

*Israel* 


