Biology subjects

Goebl, C.

Publications and source records attributed to Goebl, C..

4 recordsLinked to original sources

bioRxiv2026

Hierarchical cysteine oxidation controls reversible amyloid formation in an ankyrin repeat protein

The formation of amyloids, including functional amyloids, is observed for an increasing number of proteins but the molecular mechanisms that control this structural transition remain poorly understood. Here we report that the kinase inhibitor protein P18 (drP18) from Danio rerio (zebrafish), which contains two cysteine residues, undergoes a complex and hierarchical redox switch that strictly governs reversible amyloid formation. We identify cysteine 50 (C50) acting as a regulatory residue. Upon oxidation, C50 forms an intramolecular disulfide bond with the executioner cysteine 128 (C128), thereby blocking it. C50 can become S-glutathionylated, and upon oxidation, C128 then forms intermolecular disulfides that lead to rapid transition into amyloid fibrils. S-glutathionylation of C50 therefore enables amyloid formation of drP18 and the outcome is oxidant-dependent with diamide, hydrogen peroxide, peroxymonocarbonate and hypothiocyanous acid each leading to amyloid assembly with distinct kinetics and morphologies. These amyloids are fully reversible, where disulfide reduction is leading to disassembly. Whereas monomeric drP18 inhibits CDK4-mediated retinoblastoma phosphorylation, the amyloid conformation abolishes this inhibition, and reduction restores both structure and function. Expression of drP18 in zebrafish embryos yields Congo red-positive, oxidation-dependent aggregates in vivo. Together, our findings show that a regulatory cysteine controls an executioner cysteine to induce reversible, functional amyloid formation, revealing that proteins can encode sophisticated mechanisms to control amyloid assembly.

biochemistry↗

bioRxiv2026

Loss of cohesin subunit Stag1 in zebrafish limits cell cycle progression and is compensated by altered BMP signalling and metabolic pathways

Cohesin is a large multisubunit protein complex that plays essential roles in cell proliferation, genome organisation, and gene regulation in metazoans. Germline mutations in cohesin subunits or regulators cause a group of human developmental disorders collectively known as cohesinopathies. Increasing evidence indicates that individual cohesin subunits can confer distinct molecular functions to the complex; for example, STAG1 and STAG2 have both overlapping and non-overlapping roles in genome organisation. The zebrafish tailbud provides an excellent developmental model for investigating the coordination of cell proliferation and differentiation, processes in which cohesin has crucial functions. We previously demonstrated that loss of Stag2 disrupts Wnt signalling and mesoderm patterning in the zebrafish tailbud. Here, we show that, unlike mammals, zebrafish can tolerate complete loss of Stag1 from embryogenesis through to adulthood. In contrast to Stag2 deficiency, loss of Stag1 impairs cell cycle progression, activates p53 signalling, and induces a metabolic shift towards catabolism. BMP signalling is reduced in Stag1-deficient embryos and is accompanied by expansion of BMP antagonist chordin expression. Stag1 loss also alters chromatin accessibility at the chordin locus and affects accessibility at chromatin domain boundaries. We propose that modulation of growth and signalling pathways compensates for the absence of Stag1, allowing embryonic development to proceed correctly. Together, these findings reveal distinct contributions of Stag1 and Stag2 to cell-cycle regulation, chromatin architecture, and developmental signalling during vertebrate embryogenesis.

developmental biology↗

bioRxiv2024

Unconventional structure and function of PHD domains from Additional Sex Combs-like proteins

The Polycomb Repressive-Deubiquitinase (PR-DUB) complex removes ubiquitin from Lysine residue 119 on histone H2A (H2AK119Ub) in humans. The PR-DUB is composed of two central protein factors, the catalytic Breast Cancer type 1 susceptibility protein (BRCA1)-activating protein 1 (BAP1), and one of Additional Sex Combs-like 1-3 (ASXL1-3). A Plant Homeodomain (PHD) at the C-terminus of ASXL proteins is recurrently truncated in cancer, and was previously proposed to recognise epigenetic modifications on the N-terminal tail of histone H3. Here we demonstrate that the ASXL PHD domain lacks features required for histone tail recognition and is unable to bind histone H3 epigenetic marks. Modelling the structure of the ASXL PHD using AlphaFold3 suggests that the domain has an atypical fold and that the isolated ASXL PHD can chelate a single Zinc ion in vitro, compared to the two ions conventionally bound by PHD domains. Recently, the ASXL PHD was shown to bind an auxiliary set of PR-DUB interactors, named methyl CpG-binding domain proteins 5 (MBD5) and 6 (MBD6). We show that the ASXL PHD-MBD5 and -MBD6 complexes are stable in vitro, and surprisingly contain a composite Zinc-binding site at the interface between the two proteins. Overall, this data suggests an unconventional pairing of domains coordinate key functions of the PR-DUB -- a non-canonical PHD domain from ASXL proteins obligately partners with MBD5 and 6, which were themselves misannotated because they cannot bind to methylated DNA.

biochemistry↗

bioRxiv2019

Cysteine oxidation triggers amyloid fibril formation of the tumor suppressor p16INK4A

Accumulation of the CDK4/6 inhibitor p16INK4A in response to oncogenic transformation leads to cell cycle arrest and senescence and is therefore frequently lost in cancer. p16INK4A is also known to accumulate under conditions of oxidative stress and thus could potentially be regulated by the reversible oxidation of cysteines (redox signaling). Indeed, oxidation of the single cysteine in p16INK4A in human cells occurs under relatively mild oxidizing conditions and leads to disulfide-dependent dimerization. p16INK4A is an all alpha-helical protein, but here we report that upon cysteine-dependent dimerization, p16INK4A undergoes a dramatic structural rearrangement and forms aggregates that have the typical features of amyloid fibrils, including binding of diagnostic dyes, presence of cross-{beta} sheet structure, and typical dimensions found in electron microscopy. p16INK4A amyloid formation abolishes its function as a CDK4/6 inhibitor. Collectively, these observations mechanistically link the cellular redox state to the inactivation of p16INK4A through the formation of amyloid fibrils.

biochemistry↗