PprA Protein Inhibits DNA Strand Exchange and ATP Hydrolysis of Deinococcus RecA and Regulates the Recombination in Gamma-Irradiated Cells.

Yogendra Singh Rajpurohit,Dhirendra Kumar Sharma,Hari S Misra

doi:10.3389/fcell.2021.636178

Yogendra Singh Rajpurohit, Dhirendra Kumar Sharma + Show 1 more

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https://doi.org/10.3389/fcell.2021.636178

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Abstract

DrRecA and PprA proteins function are crucial for the extraordinary resistance to γ-radiation and DNA strand break repair in Deinococcus radiodurans. DrRecA mediated homologous recombination help in DNA strand break repair and cell survival, while the PprA protein confers radio-resistance via its roles in DNA repair, genome maintenance, and cell division. Genetically recA and pprA genes interact and constitute an epistatic group however, the mechanism underlying their functional interaction is not clear. Here, we showed the physical and functional interaction of DrRecA and PprA protein both in solution and inside the cells. The absence of the pprA gene increases the recombination frequency in gamma-irradiated D. radiodurans cells and genomic instability in cells growing under normal conditions. PprA negatively regulates the DrRecA functions by inhibiting DrRecA mediated DNA strand exchange and ATPase function in vitro. Furthermore, it is shown that the inhibitory effect of PprA on DrRecA catalyzed DNA strand exchange was not due to sequestration of homologous dsDNA and was dependent on PprA oligomerization and DNA binding property. Together, results suggest that PprA is a new member of recombination mediator proteins (RMPs), and able to regulate the DrRecA function in γ-irradiated cells by protecting the D. radiodurans genome from hyper-recombination and associated negative effects.

Highlights

An astounding gamma radiation resistance of Deinococcus radiodurans has been attributed to its efficient DNA double-strand break (DSB) repair supported by the Extended Synthesis Dependent Strand Annealing (ESDSA) mechanism and the ability to protect its biomolecules from oxidative damage (Zahradka et al, 2006; Slade et al, 2009; Misra et al, 2013)
PprA protein assists in DNA repair and cell survival of D. radiodurans recovering from ionizing radiation, and included in the DrRecA epistatic group (Narumi et al, 2004; Tanaka et al, 2004)
Deinococcus radiodurans cells have an extraordinary DNA repair capability and can endure a high level of genetic perturbation caused by ionizing radiation, desiccation, and stress-induced by cold conditions (Cox and Battista, 2005; Slade et al, 2009; Misra et al, 2013)

Summary

Introduction

An astounding gamma radiation resistance of Deinococcus radiodurans has been attributed to its efficient DNA double-strand break (DSB) repair supported by the Extended Synthesis Dependent Strand Annealing (ESDSA) mechanism and the ability to protect its biomolecules from oxidative damage (Zahradka et al, 2006; Slade et al, 2009; Misra et al, 2013). For bacterium D. radiodurans, DNA DSB repair and cell survival are heavily relying on RecA-mediated homologous (Daly et al, 1994; Daly and Minton, 1996; Zahradka et al, 2006; Slade et al, 2009). D. radiodurans lacks the LexA/RecA mediated canonical SOS regulation as DrRecA expression and/or activity is not under the control of either LexA proteins or its operon partners (CinA and LigT) (Narumi et al, 2001; Bonacossa de Almeida et al, 2002; Jolivet et al, 2006; Satoh et al, 2006). RecX of D. radiodurans is a negative regulator of recA expression as well could directly inhibit RecA activities like DNA strand exchange, ATPase activity, and LexA cleavage (Sheng et al, 2005). It is likely that some new protein regulators or other novel mechanisms may regulate DrRecA activity in the gamma-irradiated cells

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