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A SAM key domain required for enzymatic activity and allosteric activation of the Fun30 nucleosome remodeler

ABSTRACT: Fun30 is the prototype of the Fun30-SMARCAD1-ETL sub-family of nucleosome remodelers involved in DNA repair and gene silencing. These proteins appear to act as single subunit nucleosome remodelers, but their molecular mechanisms are, at this point, poorly understood. Using multiple sequence alignment and structure prediction, we identify an evolutionarily conserved domain that is modeled to contain a SAM-like fold with one long, protruding helix, which we term SAM-key. Deletion of the SAM-key within budding yeast Fun30 leads to a defect in DNA repair and gene silencing similar to that of the fun30 mutant. In vitro, Fun30 protein lacking the SAM key is able to bind nucleosomes but is deficient in DNA-stimulated ATPase activity as well as nucleosome sliding and eviction. A structural model based on AlphaFold2 prediction and verified by crosslinking-MS indicates an interaction of the long SAM-key helix with protrusion I, a subdomain located between the two ATPase lobes that is critical for control of enzymatic activity. Mutation of the interaction interface phenocopies the domain deletion with a lack of DNA-stimulated ATPase activation and a nucleosome remodeling defect, thereby confirming a role of the SAM-key helix in regulating ATPase activity. Our data thereby demonstrate a central role of the SAM-key domain in mediating the activation of Fun30 catalytic activity, thus highlighting the importance of allosteric activation for this class of enzymes.

INSTRUMENT(S): Orbitrap Exploris 480

ORGANISM(S): Saccharomyces Cerevisiae (baker's Yeast)

SUBMITTER: Barbara Steigenberger

LAB HEAD: Boris Pfander

PROVIDER: PXD037249 | Pride | 2023-07-18

REPOSITORIES: Pride

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