Quote of the Week
(March 3, 2025)

Damage to DNA is not, in the most direct sense, what proves lethal about radiation. The primary issue, instead, is damage to proteins. As long as its proteins remain functional, a cell can reassemble even a badly fractured genome; but with damaged proteins, a cell is done for, with or without an intact genome.

D. radiodurans employs a number of strategies for preserving its rather commonplace “proteome”, or total inventory of proteins. These strategies include (1) preventing the oxidative damage that results from radiation, a goal it achieves in good part by means of an especially rich supply of antioxidants; (2) eliminating, before they can cause mischief, any proteins that do get damaged, while recycling their constituents; (3) scavenging amino acids and peptides (protein constituents) from the local environment, a capability that, together with the recycling, supports (4) newly synthesizing any proteins that need replenishing.

The proteome thus preserved is then able to go about the task of reconstructing a shattered genome — a task whose complexity at the molecular level is stunning. (Many a bright but befuddled graduate student has twisted his imagination into knots while trying to picture the various textbook processes of DNA damage repair in human cells.) Nevertheless, the task is accomplished in the cells of all organisms. What distinguishes D. radiodurans is its ability to carry out this task to an exceptional degree by maintaining its store of proteins intact under extreme duress.

(from Chapter 8, “The Mystery of an Unexpected Coherence”, in Organisms and Their Evolution — Agency and Meaning in the Drama of Life)

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