Abstract
Tardigrades, also known as water bears, are animals that can survive extreme conditions. The tardigrade Ramazzottius varieornatus contains a unique nuclear protein termed Dsup, for damage suppressor, which can increase the resistance of human cells to DNA damage under conditions, such as ionizing radiation or hydrogen peroxide treatment, that generate hydroxyl radicals. Here we find that R. varieornatus Dsup is a nucleosome-binding protein that protects chromatin from hydroxyl radicals. Moreover, a Dsup ortholog from the tardigrade Hypsibius exemplaris similarly binds to nucleosomes and protects DNA from hydroxyl radicals. Strikingly, a conserved region in Dsup proteins exhibits sequence similarity to the nucleosome-binding domain of vertebrate HMGN proteins and is functionally important for nucleosome binding and hydroxyl radical protection. These findings suggest that Dsup promotes the survival of tardigrades under diverse conditions by a direct mechanism that involves binding to nucleosomes and protecting chromosomal DNA from hydroxyl radicals.
Highlights
Tardigrades, which are known as water bears or moss piglets, are small invertebrate animals that are found in marine, freshwater, and terrestrial habitats throughout the Earth
To test the relevance of these findings to other tardigrades, we examined the properties of a Dsup-like protein from H. exemplaris, and found that this protein appears to be an ortholog of R. varieornatus Dsup
We will refer to the R. varieornatus Dsup protein as ‘Rv Dsup’
Summary
Tardigrades, which are known as water bears or moss piglets, are small invertebrate animals that are found in marine, freshwater, and terrestrial habitats throughout the Earth (reviewed in Guidetti et al, 2012; Møbjerg et al, 2011; Weronika and Łukasz, 2017). They are typically about 0.1 to 1 mm in length, and comprise a head segment in addition to four body segments that each contains two legs with claws. Tardigrades are resistant to extreme conditions of heat, cold, vacuum, pressure, radiation, and chemical treatments. The analysis of their singular features should lead to significant new biological insights
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