Biology subjects

Bardwell, L.

Publications and source records attributed to Bardwell, L..

4 recordsLinked to original sources

bioRxiv2026

Cyclin B3-CDK1 couples translational de-repression to embryonic mitoses via OMA protein degradation in C. elegans.

During early embryogenesis, gene expression relies on maternally loaded mRNAs whose translation is controlled by RNA binding proteins. Here, we identify a critical role for the cyclin B3-CDK1 complex, known for its function in mitosis, in driving early embryonic gene expression in C. elegans. The cyclin B3-CDK1 complex works by marking the RNA binding OMA proteins (OMA-1 and OMA-2) for degradation, which ensures the de-repression and translation of their target mRNAs. OMA protein degradation relies on cyclin B3s conserved phosphate-binding pocket, which promotes multi-site OMA phosphorylation and the generation of phospho-degrons. Notably, the phosphate-binding pocket of cyclin B3 does not substantially contribute to its mitotic roles, indicating that the mitotic and translational functions of the cyclin B3-CDK1 complex are separable. These findings establish that embryonic activation of the cyclin B3-CDK1 complex drives both mitotic divisions and mRNA de-repression, which ensures that cell division is coupled to the early gene expression program in development.

developmental biology↗

bioRxiv2026

AlphaFold3 predictions of novel GLI-SUFU interfaces identify binding-defective SUFU missense variants from medulloblastoma and Gorlin Syndrome patients

The tumor suppressor SUFU is a key negative regulator of oncogenic GLI transcription factors. SUFU mutations predispose to medulloblastoma and can cause Gorlin and Joubert syndromes. Limited structural information is available on the GLI-SUFU complex, contributing to the fact that the vast majority of SUFU missense variants sequenced from affected patients are of unknown clinical significance. Using AlphaFold3 and complementary computational analysis, we predicted structures of the three human GLI-SUFU complexes and the orthologous Drosophila Ci-Sufu complex, revealing previously unrecognized contact interfaces. By site-directed mutagenesis and GLI-SUFU binding assays, we validated the importance of key interface residues, many of which are mutated in familial medulloblastoma and Gorlin syndrome. These findings provide new structure-function insights into a signaling complex mutated in cancer and rare congenital diseases, and offer an expanded framework for interpreting clinically observed SUFU variants and mechanisms that tune SUFU repression. TeaserAI-powered modeling plus experimental validation reveal new GLI-SUFU interfaces linked to cancer and congenital mutations.

biochemistry↗

bioRxiv2022

The WW domain of IQGAP1 binds directly to the p110α catalytic subunit of PI 3-kinase

IQGAP1 is a multi-domain cancer-associated protein that serves as a scaffold protein for multiple signaling pathways. Numerous binding partners have been found for the calponin homology, IQ and GAP-related domains in IQGAP1. Identification of a binding partner for its WW domain has proven elusive, however, even though a cell-penetrating peptide derived from this domain has marked anti-tumor activity. Here, using in vitro binding assays with human proteins and co-precipitation from human cells, we show that the WW domain of human IQGAP1 binds directly to the p110 catalytic subunit of phosphoinositide 3-kinase (PI3K). In contrast, the WW domain does not bind to ERK1/2, MEK1/2, or the p85 regulatory subunit of PI3K when p85 is expressed alone. However, the WW domain is able to bind to the p110/p85 heterodimer when both subunits are co-expressed, as well as to the mutationally activated p110/p65 heterodimer. We present a model of the structure of the IQGAP1 WW domain, and experimentally identify key residues in the hydrophobic core and beta strands of the WW domain that are required for binding to p110. These findings contribute to a more precise understanding of IQGAP1-mediated scaffolding, and of how IQGAP1-derived therapeutic peptides might inhibit tumorigenesis.

biochemistry↗

bioRxiv2021

ERK2 MAP kinase regulates SUFU binding by multisite phosphorylation of GLI1

There is considerable evidence that crosstalk between the Hedgehog and MAPK signaling pathways occurs in several types of cancer, and contributes to the emergence of clinical resistance to Hedgehog pathway inhibitors. Here we show that MAP kinase-mediated phosphorylation weakens the binding of the GLI1 transcription factor to its negative regulator SUFU. ERK2 phosphorylates GLI1 on three evolutionarily-conserved target sites (S102, S116 and S130) located near the high-affinity binding site for SUFU; these phosphorylations cooperate to weaken the affinity of GLI1-SUFU binding by over 25 fold. Phosphorylation of any one, or even any two, of the three sites does not result in the level of SUFU release seen when all three sites are phosphorylated. Tumor-derived mutations in R100 and S105, residues bordering S102, also diminish SUFU binding, collectively defining a novel evolutionarily-conserved SUFU-affinity-modulating region. In cultured mammalian cells, GLI1 variants containing phosphomimetic substitutions of S102, S116 and S130 displayed an increased ability to drive transcription. We conclude that of multisite phosphorylation of GLI1 by ERK2 or other MAP kinases weakens GLI1-SUFU binding, thereby facilitating GLI1 activation and contributing to both physiological and pathological crosstalk.

cell biology↗