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Published on: May 31, 2013
A bacterial expression cloning screen reveals single-stranded DNA-binding proteins as potent desicco-protectants
Jonathan D Hibshman1, Courtney M Clark-Hachtel1, Kerry S Bloom2
1Biology Department, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Abstract:
Desiccation kills most cells. Some proteins have been identified to help certain cells survive desiccation, but many protein protectants are likely to be unknown. Moreover, the mechanisms ensuring protection of key cellular components are incompletely understood. We devised an expression-cloning approach to discover further protectants. We expressed cDNA libraries from two species of tardigrades in E. coli, and we subjected the bacteria to desiccation to select for survivors. Sequencing the populations of surviving bacteria revealed enrichment of mitochondrial single-stranded DNA-binding proteins (mtSSBs) from both tardigrade species. Expression of mtSSBs in bacteria improved desiccation survival as strongly as the best tardigrade protectants known to date. We found that DNA-binding activity of mtSSBs was necessary and sufficient to improve the desiccation tolerance of bacteria. Although tardigrade mtSSBs were among the strongest protectants we found, single-stranded DNA binding proteins in general offered some protection. These results identify single-stranded DNA-binding proteins as potent desicco-protectants.
Insights
Tardigrade mitochondrial single-stranded DNA-binding proteins (mtSSBs) protect bacteria from drying out. These DNA-binding proteins are potent desicco-protectants, enhancing cellular survival during dehydration.
Area of Science:
- Biochemistry
- Molecular Biology
- Extremophile Research
Background:
- Desiccation (drying out) is a major cause of cell death.
- While some protein protectants are known, many remain undiscovered.
- Mechanisms of cellular protection during dehydration are not fully understood.
Purpose of the Study:
- To discover novel protein protectants against desiccation.
- To investigate the role of specific proteins in enhancing desiccation tolerance.
- To elucidate the mechanisms underlying protection from drying.
Main Methods:
- Utilized an expression-cloning approach to identify protective proteins.
- Expressed tardigrade cDNA libraries in E. coli bacteria.
- Subjected engineered bacteria to desiccation and sequenced survivors to identify enriched genes.
Main Results:
- Mitochondrial single-stranded DNA-binding proteins (mtSSBs) from tardigrades were significantly enriched in surviving bacteria.
- Tardigrade mtSSBs strongly enhanced bacterial desiccation survival, comparable to known protectants.
- The DNA-binding activity of mtSSBs was essential for their protective function.
Conclusions:
- Identified single-stranded DNA-binding proteins, particularly mtSSBs, as potent desicco-protectants.
- Demonstrated that mtSSBs protect cells by binding to DNA.
- Highlighted the potential of single-stranded DNA-binding proteins for improving desiccation tolerance in various organisms.
