RESUMO
The RNF43_p.G659fs mutation occurs frequently in colorectal cancer, but its function remains poorly understood and there are no specific therapies directed against this alteration. In this study, we find that RNF43_p.G659fs promotes cell growth independent of Wnt signaling. We perform a drug repurposing library screen and discover that cells with RNF43_p.G659 mutations are selectively killed by inhibition of PI3K signaling. PI3K/mTOR inhibitors yield promising antitumor activity in RNF43659mut isogenic cell lines and xenograft models, as well as in patient-derived organoids harboring RNF43_p.G659fs mutations. We find that RNF43659mut binds p85 leading to increased PI3K signaling through p85 ubiquitination and degradation. Additionally, RNA-sequencing of RNF43659mut isogenic cells reveals decreased interferon response gene expression, that is reversed by PI3K/mTOR inhibition, suggesting that RNF43659mut may alter tumor immunity. Our findings suggest a therapeutic application for PI3K/mTOR inhibitors in treating RNF43_p.G659fs mutant cancers.
Assuntos
Neoplasias Colorretais , Fosfatidilinositol 3-Quinases , Serina-Treonina Quinases TOR , Ubiquitina-Proteína Ligases , Linhagem Celular Tumoral , Neoplasias Colorretais/tratamento farmacológico , Neoplasias Colorretais/genética , Neoplasias Colorretais/metabolismo , Humanos , Mutação , Fosfatidilinositol 3-Quinases/genética , Serina-Treonina Quinases TOR/genética , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismoRESUMO
Although bespoke, sequence-specific proteases have the potential to advance biotechnology and medicine, generation of proteases with tailor-made cleavage specificities remains a major challenge. We developed a phage-assisted protease evolution system with simultaneous positive and negative selection and applied it to three botulinum neurotoxin (BoNT) light-chain proteases. We evolved BoNT/X protease into separate variants that preferentially cleave vesicle-associated membrane protein 4 (VAMP4) and Ykt6, evolved BoNT/F protease to selectively cleave the non-native substrate VAMP7, and evolved BoNT/E protease to cleave phosphatase and tensin homolog (PTEN) but not any natural BoNT protease substrate in neurons. The evolved proteases display large changes in specificity (218- to >11,000,000-fold) and can retain their ability to form holotoxins that self-deliver into primary neurons. These findings establish a versatile platform for reprogramming proteases to selectively cleave new targets of therapeutic interest.
Assuntos
Toxinas Botulínicas/metabolismo , Evolução Molecular Direcionada , Engenharia de Proteínas , Animais , Bacteriófago M13/genética , Toxinas Botulínicas/química , Toxinas Botulínicas/genética , Domínio Catalítico , Linhagem Celular , Células Cultivadas , Humanos , Mutação , Neurônios/metabolismo , PTEN Fosfo-Hidrolase/metabolismo , Biblioteca de Peptídeos , Domínios Proteicos , Proteínas R-SNARE/metabolismo , Ratos , Seleção Genética , Especificidade por Substrato , Proteína 2 Associada à Membrana da Vesícula/metabolismoRESUMO
Histone post-translational modifications (PTMs) carry an epigenetic layer of message to regulate diverse cellular processes at the chromatin level. Many of these PTMs are selectively recognized by dedicated effector proteins for normal cell growth and development, while dysregulation of these recognition events is often implicated in human diseases, notably cancer. Thus, it is fundamentally important to elucidate the regulatory mechanism(s) underlying the readout of PTMs on histones. The Yaf9, ENL, AF9, Taf14, Sas5 (YEATS) domain is an emerging reader module that selectively recognizes histone lysine acylation with a preference for crotonylation over acetylation. In the review, we discuss the recognition of histone acylations by the YEATS domain and the biological significance of this readout from multiple perspectives.
Assuntos
Proteínas Cromossômicas não Histona/metabolismo , Regulação da Expressão Gênica , Histonas/metabolismo , Neoplasias/fisiopatologia , Processamento de Proteína Pós-Traducional , Acilação , Humanos , Ligação ProteicaRESUMO
The decoding of histone post-translational modifications by chromatin-binding modules ("readers") constitutes one major mechanism of epigenetic regulation. Nuclear antigen Sp100 (SPECKLED, 100 kDa), a constitutive component of the promyelocytic leukemia nuclear bodies, plays key roles in intrinsic immunity and transcriptional repression. Sp100C, a splicing isoform specifically up-regulated upon interferon stimulation, harbors a unique tandem plant homeodomain (PHD) finger and bromodomain at its C terminus. Combining structural, quantitative binding, and cellular co-localization studies, we characterized Sp100C PHD finger as an unmethylated histone H3 Lys(4) (H3K4me0) reader that tolerates histone H3 Thr(3) phosphorylation (H3T3ph), histone H3 Lys(9) trimethylation (H3K9me3), and histone H3 Ser(10) phosphorylation (H3S10ph), hallmarks associated with the mitotic chromosome. In contrast, whereas H3K4me0 reader activity is conserved in Sp140, an Sp100C paralog, the multivalent tolerance of H3T3ph, H3K9me3, and H3S10ph was lost for Sp140. The complex structure determined at 2.1 Šrevealed a highly coordinated lysine ϵ-amine recognition sphere formed by an extended N-terminal motif for H3K4me0 readout. Interestingly, reader pocket rigidification by disulfide bond formation enhanced H3K4me0 binding by Sp100C. An additional complex structure solved at 2.7 Šrevealed that H3T3ph is recognized by the arginine residue, Arg(713), that is unique to the PHD finger of Sp100C. Consistent with a restrictive cellular role of Sp100C, these results establish a direct chromatin targeting function of Sp100C that may regulate transcriptional gene silencing and promyelocytic leukemia nuclear body-mediated intrinsic immunity in response to interferon stimulation.