Biology subjects

Hoeg, L.

Publications and source records attributed to Hoeg, L..

4 recordsLinked to original sources

bioRxiv2023

Loss of Nkd1 is dominant over loss of Axin2 in regulating Wnt signaling

Wnt signaling is a crucial developmental pathway involved in early development as well as stem cell maintenance in adults and its misregulation leads to numerous diseases. Thus, understanding the regulation of this pathway becomes vitally important. Axin2 and Nkd1 are widely utilized negative feedback regulators in Wnt signaling where Axin2 functions to destabilize cytoplasmic {beta}-catenin, and Nkd1 functions to inhibit the nuclear localization of {beta}-catenin. Here, we set out to further understand how Axin2 and Nkd1 regulate Wnt signaling by creating axin2-/-, nkd1-/- single mutants and axin2-/-;nkd1-/- double mutant zebrafish using sgRNA/Cas9. All three Wnt regulator mutants were viable and had impaired heart looping, neuromast migration defects, and behavior abnormalities in common, but there were no signs of synergy in the axin2-/-;nkd1-/- double mutants. Further, Wnt target gene expression by qRT-PCR, and RNA-seq analysis and protein expression by mass spectrometry demonstrated that the double axin2-/-;nkd1-/- mutant resembled the nkd1-/- phenotype demonstrating that Axin2 functions upstream of Nkd1 and that loss of Nkd1 is epistatic to the loss of Axin2. In support of this, the data further demonstrates that Axin2 uniquely alters the properties of {beta}-catenin-dependent transcription having novel readouts of Wnt activity compared to nkd1-/- or the axin2-/-;nkd1-/- double mutant. We also tested the sensitivity of the Wnt regulator mutants to exacerbated Wnt signaling, where the single mutants displayed characteristic heightened Wnt sensitivity, resulting in an eyeless phenotype. Surprisingly, this phenotype was rescued in the double mutant, where we speculate that cross-talk between Wnt/{beta}-catenin and Wnt/Planar Cell Polarity pathways could lead to altered Wnt signaling in some scenarios. Collectively, the data emphasizes both the commonality and the complexity in the feedback regulation of Wnt signaling.

developmental biology↗

bioRxiv2023

Chemogenetic profiling of ubiquitin-like modifier pathways identifies NFATC2IP as a mediator of SUMO-dependent genome integrity

The post-translational modification of proteins by ubiquitin and ubiquitin-like polypeptides controls multiple cellular processes including the abundance of a large fraction of the proteome. We applied genome-scale CRISPR/Cas9 screens to elucidate the genetic architecture of the response to inhibition of ubiquitin, NEDD8 and SUMO conjugation pathways as well as inhibition of the p97/VCP segregase. This effort identified 395 genes whose disruption alters the fitness of human cells when faced with perturbations in these pathways. We validated that the TMED2 and TMED10 proteins, which are localized to the secretory pathway, promote resistance to p97/VCP inhibition and also characterized NFATC2IP, an evolutionarily conserved protein harboring SUMO-like domains as a major player in promoting genomic integrity when SUMOylation is inhibited. We propose that NFATC2IP acts in interphase cells to promote the SUMO-dependent E3 ligase activity of the SMC5/SMC6 complex, which is critical for SUMO-dependent genome integrity.

molecular biology↗

bioRxiv2023

An AlphaFold2 map of the 53BP1 pathway identifies a direct SHLD3-RIF1 interaction critical for DNA repair activity

53BP1 is a chromatin-binding DNA repair protein that promotes DNA double-strand break repair through recruitment of downstream effectors including RIF1, shieldin, and CST. The structural basis of the protein-protein interactions within the 53BP1-RIF1-shieldin-CST pathway that are essential for its DNA repair activity are largely unknown. Here we used AlphaFold2-Multimer (AF2) to predict all possible pairwise combinations of proteins within this pathway and provide structural models of seven previously characterized interactions. This analysis also predicted an entirely novel binding interface between the HEAT-repeat domain of RIF1 and the eIF4E-like domain of SHLD3. Extensive interrogation of this interface through both in vitro pulldown analysis and cellular assays supports the AF2-predicted model and demonstrates that RIF1-SHLD3 binding is essential for shieldin recruitment to sites of DNA damage, and for its role in antibody class switch recombination. Direct physical interaction between RIF1 and SHLD3 is therefore essential for 53BP1-RIF1-shieldin-CST pathway activity.

molecular biology↗

bioRxiv2022

Genome-scale mapping of DNA damage suppressors identifies GNB1L as essential for ATM and ATR biogenesis

To maintain genome integrity, cells must avoid DNA damage by ensuring the accurate duplication of the genome and by having efficient repair and signaling systems that counteract the genome-destabilizing potential of DNA lesions. To uncover genes and pathways that suppress DNA damage in human cells, we undertook genome-scale CRISPR/Cas9 screens that monitored the levels of DNA damage in the absence or presence of DNA replication stress. We identified 160 genes in RKO cells whose mutation caused high levels of DNA damage in the absence of exogenous genotoxic treatment. This list was highly enriched in essential genes, highlighting the importance of genomic integrity for cellular fitness. Furthermore, the majority of these 160 genes are involved in a limited set of biological processes related to DNA replication and repair, nucleotide biosynthesis, RNA metabolism and iron sulfur cluster biogenesis, suggesting that genome integrity may be insulated from a wide range of cellular processes. Among the many genes identified and validated in this study, we discovered that GNB1L, a schizophrenia/autism-susceptibility gene implicated in 22q11.2 syndrome, protects cells from replication catastrophe promoted by mild DNA replication stress. We show that GNB1L is involved in the biogenesis of ATR and related phosphatidylinositol 3-kinase-related kinases (PIKKs) through its interaction with the TTT co-chaperone complex. These results implicate PIKK biogenesis as a potential root cause for the neuropsychiatric phenotypes associated with 22q11.2 syndrome. The phenotypic mapping of genes that suppress DNA damage in human cells therefore provides a powerful approach to probe genome maintenance mechanisms.

molecular biology↗