Biology subjects

Faesen, A.

Publications and source records attributed to Faesen, A..

2 recordsLinked to original sources

bioRxiv2022

Metamorphic proteins at the basis of human autophagy initiation and lipid transfer

Autophagy is a conserved intracellular degradation pathway that uses de novo doublemembrane vesicle (autophagosome) formation to target a wide range of cytoplasmic material for lysosomal degradation. In multicellular organisms, autophagy initiation requires the timely assembly of a contact site between the ER and the nascent autophagosome. Here, we report the in vitro reconstitution of a full-length sevensubunit human autophagy initiation supercomplex and found at its core ATG13-101 and transmembrane protein ATG9. Assembly of this core complex requires the rare ability of ATG13 and ATG101 to adopt topologically distinct folds. The slow spontaneous conversion between folds creates a rate-limiting step to regulate selfassembly of the super-complex. The interaction of the core complex with ATG2-WIPI4 enhances tethering of membrane vesicles and accelerates lipid transfer of ATG2 by both ATG9 and ATG13-101. Our work uncovers the molecular basis of the contact site and its assembly mechanisms imposed by the metamorphosis of ATG13-101 to regulate autophagosome biogenesis in space and time.

biochemistry↗

bioRxiv2022

Molecular insights into human Shieldin complex assembly and recruitment to DSBs

The Shieldin complex represses end resection at DNA double-strand breaks (DSBs) and thereby serves as a pro-non homologous end joining (NHEJ) factor in the G1 phase of the cell cycle. Its components SHLD1, SHLD2, SHLD3 and REV7 are recruited in a hierarchical fashion. SHLD3 and REV7 localize first to DSBs, while the subsequently recruited SHLD2 is the only known DNA binding protein in the complex. The molecular details of the initial recruitment of SHLD3 and REV7, and the subsequent assembly of Shieldin on DSBs are unclear. Here, we report the identification of a promiscuous DNA binding domain in the C-terminal half of SHLD3. At the N-terminus, SHLD3 interacts with a dimer of REV7 molecules. We show that the interaction between SHLD3 and the first REV7 is remarkably slow, which is likely due to the substantial activation energy required to remodel mobile structural elements within the REV7 molecule to allow for binding to SHLD3. In contrast, the interaction between SHLD3 and SHLD2 with a second REV7 molecule is fast and does not require structural remodelling. Overall, these results provide insights into the rate-limiting step of the molecular assembly and recruitment of Shieldin complex at DNA DSBs.

biochemistry↗