LAUSR

Almost all organisms express proteins that coat and organize DNA (nucleoid-associated proteins or NAPs). NAPs (such as histones in eukaryotes) play many roles, from scaffolding and protecting the DNA to regulating transcription, replication and epigenetic signaling, making it difficult to reconstruct their evolutionary histories and original functions. Here comparative genomics with protein abundance measurements across a range of archaea reveal a wide spectrum of NAP levels strongly correlated with growth temperature. Surprisingly, a family within the large taxonomic grouping of the Diaforarchaea appear to encode no NAPs at all. This work suggests that DNA-binding activities evolved primarily as a way to cope with heat stress, with implications for the evolution of chromatin in other archaea and a thermophilic origin for the first eukaryotes.