RNase Z from Deinococcus radiodurans couples tRNA processing with stress-responsive mRNA and sRNA turnover

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• RNase Z is a metallo-dependent endoribonuclease crucial for tRNA 3'-end processing in bacteria.
• Its role in RNA turnover during stress responses is not fully understood.
• Deinococcus radiodurans is known for its extreme radiation resistance, making its RNA processing mechanisms of interest.

Purpose of the Study:

• To biochemically characterize RNase Z from Deinococcus radiodurans (DrRNase Z).
• To investigate the regulatory functions and substrates of DrRNase Z, particularly under stress conditions.
• To elucidate the role of DrRNase Z in maintaining RNA homeostasis in D. radiodurans.

Main Methods:

• Cloning, overexpression, and purification of the rnz gene and recombinant DrRNase Z.
• ICP-MS analysis to determine Zn2+ ion coordination.
• In vitro assays using precursor tRNAArg, katA mRNA, and IGR_1612 small RNA substrates.
• Analysis of rnz transcript levels under γ-irradiation and oxidative stress.

Main Results:

• DrRNase Z requires Zn2+ for phosphodiesterase activity, coordinating two Zn2+ ions per monomer.
• The enzyme efficiently processes precursor tRNAArg but not mature tRNA.
• DrRNase Z cleaves oxidative stress-inducible katA mRNA and stress-responsive IGR_1612 sRNA.
• rnz transcript levels decrease significantly under γ-irradiation and oxidative stress.

Conclusions:

• DrRNase Z plays a dual role in tRNA maturation and the turnover of stress-induced mRNAs and sRNAs.
• This enzyme contributes to restoring RNA homeostasis in D. radiodurans following stress exposure.
• DrRNase Z is a key factor in bacterial stress response and RNA management.