Biology subjects

Penn, L. Z.

Publications and source records attributed to Penn, L. Z..

5 recordsLinked to original sources

bioRxiv2025

CHD1 is a synthetic lethal vulnerability in MYC-driven breast cancer

The MYC transcription factor is a key regulator of growth during development and a potent cancer driver when its expression is dysregulated. Strategies to inhibit MYC oncogenic activity would mark a significant advance, but decades of efforts to target MYC directly have not been fruitful. Understanding how MYC drives transformation and tumor growth may provide new therapeutic avenues in a variety of cancers. By intersecting two independent genome-wide screens, we identified loss of the chromatin remodeler Chromodomain-Helicase DNA-binding 1 (CHD1) as a potential synthetic lethal target in MYC-driven breast cancer. Knockdown of CHD1 in a xenograft model of MYC-driven breast cancer suppresses tumor growth in vivo. In tissue culture models, we found that knockdown of CHD1 suppresses cell proliferation and induces cell death, specifically when MYC is overexpressed. Mechanistically, we found that CHD1 is required to maintain an open chromatin landscape and a transcriptional program associated with cancer progression in MYC overexpressing breast cells. Follow-up experiments indicate that this synthetic lethality may arise from nucleolar stress and p53 activation. These findings provide new insights on the chromatin-level regulation of MYC-driven breast cancer and uncover CHD1 as a novel synthetic vulnerability and potential therapeutic target.

cancer biology↗

bioRxiv2024

Structural basis of TMPRSS11D specificity and autocleavage activation

Transmembrane Protease, Serine-2 (TMPRSS2) and TMPRSS11D are human proteases that enable SARS-CoV-2 and Influenza A/B virus infections, but their biochemical mechanisms for facilitating viral cell entry remain unclear. We demonstrate these proteases can spontaneously and efficiently cleave their own zymogen activation motifs, thereby activating their wider protease activity on other cellular substrates. We determined TMPRSS11D co-crystal structures in complexes with a native TMPRSS11D zymogen activation motif and with an engineered activation motif, providing insights into TMPRSS11D autocleavage activation and revealing unique regions of its substrate binding cleft. We further show that a protease inhibitor that underwent clinical trials for TMPRSS2-targeted COVID-19 therapy, nafamostat mesylate, was rapidly cleaved by TMPRSS11D and converted to low activity derivatives. These insights into human protease viral tropism and into liabilities with existing human serine protease inhibition strategies will guide future drug discovery campaigns for these targets.

biochemistry↗

bioRxiv2022

SLC3A2 N-glycosylation and alternate evolutionary trajectories for amino acid metabolism

SLC3A2 (4F2hc, CD98) is an adaptor to the SLC7A exchangers and has undergone extensive repositioning of N-glycosylation sites with vertebrate evolution, presumably in synchrony with the species-specific demands of metabolism. The SLC3A2*SLC7A5 heterodimer imports essential amino acids (AA) and thereby stimulates mTOR signaling, while SLC3A2*SLC7A11 imports cystine required for glutathione synthesis and mitigation of oxidative stress. Analysis of SLC3A2 N-glycans revealed stable site-specific profiles of Golgi remodeling, apart from the conserved N365 site where branching and poly-N-acetylglucosamine content were sensitive to the insertion of lost ancestral sites and to metabolism. N-glycans at N381 and N365 stabilized SLC3A2 in the galectin lattice and opposed endocytosis, while N365 which is nearest the membrane, also promoted down-regulation by galectin-driven clathrin-independent endocytosis (glycolipid-lectin GL-Lect). This is the first report of both positive and negative regulation by galectin binding to N-glycans that are strategically positioned in the same membrane glycoproteins. Proteomics analysis in SLC3A2 mutant HeLa cells with induced re-expression of SLC3A2 as bait revealed the canonical non-N-glycosylated interactors, SLC7A5 and SLC7A11 exchangers, but also AA transporters that were dependent on SLC3A2 N-glycosylation, and are themselves, N-glycosylated AA/Na+ symporters (SLC7A1, SLC38A1, SLC38A2, SLC1A4, SLC1A5). The results suggest that the N-glycans on SLC3A2 regulate clustering of SLC7A exchangers with AA/Na+ symporters, thereby promoting Gln/Glu export-driven import of essential AA and cystine, with the potential to adversely impact redox balance. The evolution of modern birds (Neoaves) led to improved control of bioenergetics with the loss of genes including SLC3A2, SLC7A-5, -7, -8, -10, BCAT2, KEAP1, as well as duplications of SLC7A9, SLC7A11 and the Golgi branching enzymes MGAT4B and MGAT4C known to enhance affinities for galectins. Analyzing the fate of these and other genes in the down-sized genomes of birds, spanning [~]10,000 species and >100 Myr of evolution, may reveal the mystery of their longevity with prolonged vitality. Key PointsO_LIGolgi N-glycan remodeling at each site on SLC3A2 differs with the microenvironment. C_LIO_LIThe galectin lattice and GL-Lect mediated endocytosis act as opposing forces on trafficking, controlled by N-glycans at the distal N381 and membrane proximal N365 sites, respectively. C_LIO_LIMutation at N381 or N365 decreased SLC3A2 association with SLC7A5, SLC7A11 and N-glycosylated AA/Na+ symporters as well as the capacity to mitigate stress. C_LIO_LIClustering of SLC3A2*SLC7A exchangers, with AA/Na+ symporter and ATPase Na+/K+ exchanger promotes growth but continuously consumes ATP in non-proliferating cells. C_LIO_LIBird evolution has improved bioenergetics with the deletion of SLC3A2 and associated transporters; - replaced by transporters of keto acids and a re-enforced galectin lattice. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=73 SRC="FIGDIR/small/516651v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@1cb7958org.highwire.dtl.DTLVardef@18ba32dorg.highwire.dtl.DTLVardef@861269org.highwire.dtl.DTLVardef@22df0e_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2021

The PNUTS-PAD domain recruits MYC to the PNUTS:PP1 phosphatase complex via the oncogenic MYC-MB0 region

Despite MYC dysregulation in most human cancers, strategies to target this potent oncogenic driver remains an urgent unmet need. Recent evidence shows the PP1 phosphatase and its regulatory subunit PNUTS control MYC phosphorylation and stability, however the molecular basis remains unclear. Here we demonstrate that MYC interacts directly with PNUTS through the MYC homology Box 0 (MB0), a highly conserved region recently shown to be important for MYC oncogenic activity. MB0 interacts with PNUTS residues 1-148, a functional unit here termed, PNUTS amino-terminal domain (PAD). Using NMR spectroscopy we determined the solution structure of PAD, and characterised its interaction with MYC. Point mutations of residues at the MYC-PNUTS interface significantly weaken their interaction both in vitro and in vivo. These data demonstrate the MB0 binding pocket of the PAD represents an attractive site for pharmacological disruption of the MYC-PNUTS interaction. In BriefSolving the structure of MYC-PNUTS direct interaction reveals how the intrinsically disordered MYC-Box0 (MB0) region anchors into a binding pocket in the N-terminal PAD domain of PNUTS. These data provide insight into the molecular mechanism of how the PNUTS:PP1 phosphatase complex regulates MYC phosphorylation. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=197 SRC="FIGDIR/small/470928v1_ufig1.gif" ALT="Figure 1"> View larger version (86K): org.highwire.dtl.DTLVardef@179b89corg.highwire.dtl.DTLVardef@47338eorg.highwire.dtl.DTLVardef@89b6f4org.highwire.dtl.DTLVardef@14a80bd_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIA region critical for MYC oncogenesis, MYC-Box0 (MB0), directly interacts with PNUTS C_LIO_LIPNUTS amino-terminal domain (PAD) is a structural domain that interacts with MYC MB0 C_LIO_LIMutation of single residues at the interaction interface disrupts MYC-PNUTS binding in cells C_LIO_LIMYC-PNUTS binding releases MYC intramolecular interactions to enable PP1substrate access C_LI

cancer biology↗

bioRxiv2018

Modeling the MYC-driven normal-to-tumour switch in breast cancer.

The potent MYC oncoprotein is deregulated in many human cancers, including breast carcinoma, and is associated with aggressive disease. To understand the mechanisms and vulnerabilities of MYC-driven breast cancer, we have generated an in vivo model that mimics human disease in response to MYC deregulation. MCF10A cells ectopically expressing a common breast cancer mutation in the PI3 kinase pathway (PIK3CAH1047R) lead to the development of organized acinar structures in mice. However, expressing both PIK3CAH1047R and deregulated-MYC lead to the development of invasive ductal carcinoma, thus creating a model in which a MYC-dependent normal-to-tumour switch occurs in vivo. These MYC-driven tumors exhibit classic hallmarks of human breast cancer at both the pathological and molecular levels. Moreover, tumour growth is dependent upon sustained deregulated MYC expression, further demonstrating addiction to this potent oncogene and regulator of gene transcription. We therefore provide a MYC-dependent human model of breast cancer which can be assayed for in vivo tumour initiation, proliferation, and transformation from normal breast acini into invasive breast carcinoma. Taken together, we anticipate that this novel MYC-driven transformation model will be a useful research tool to both better understand MYCs oncogenic function and identify therapeutic vulnerabilities.

cancer biology↗