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Palmer, A. G.

Publications and source records attributed to Palmer, A. G..

2 recordsLinked to original sources
bioRxiv2020

Cadherin-11 dimerization multi-site kinetics: combined partial unfolding and strand-swapping

Cadherin extracellular domain 1 (EC1) mediates homophilic dimerization in adherens junctions. Conserved Trp2 and Trp4 residues in type II cadherins anchor the EC1 A-strand intermolecularly in strand-swapped dimers. Herein, NMR spectroscopy is used to elucidate the roles of Trp2 and Trp4 in Cadherin-11 dimerization. The monomeric state, with the A-strand and Trp side chains packed intramolecularly, is in equilibrium with sparsely populated partially and fully A-strand-exposed states, in which Trp2 (and Trp4, respectively) side-chain packing is disrupted. Exchange kinetics between the major state and the partially (fully) A-strand-exposed state is slow-intermediate (intermediate-fast). A separate very fast process exchanges ordered and random-coil BC loop conformations with populations dependent on A-strand exposure and dimerization status. Additionally, very slow processes connect the folded A-strand-exposed conformation to partially unfolded states, which may represent additional domain-swapping intermediates. The dimerization mechanism of type II cadherins is revealed as coupled folding and strand-swapping.

biophysics↗
bioRxiv2020

Asterix/Gtsf1 links tRNAs and piRNA silencing of retrotransposons

The piRNA pathway safeguards genomic integrity by silencing transposable elements in the germline. While Piwi is the central piRNA factor, others including Asterix/Gtsf1 have also been demonstrated to be critical for effective silencing. Here, using eCLIP with a custom informatic pipeline, we show that Asterix/Gtsf1 specifically binds tRNAs in cellular contexts. We determined the structure of mouse Gtsf1 by NMR spectroscopy and identified the RNA binding interface on the proteins first zinc finger, which was corroborated by biochemical analysis as well as cryo-EM structures of Gtsf1 in complex with co-purifying tRNA. We further show that LTR retrotransposons are preferentially de-repressed in Asterix mutants. Given the role of tRNAs as LTR retrotransposon primers, our work implicates Asterix/Gtsf1 as exploiting tRNA dependence to identify transposon transcripts and promote piRNA silencing.

biochemistry↗