RESUMO
BACKGROUND: Although the founding members of the INhibitor of Growth (ING) family of histone mark readers, ING1 and ING2, were defined as tumour suppressors in animal models, the role of other ING proteins in cellular proliferation and cancer progression is unclear. METHODS: We transduced ex vivo benign prostate hyperplasia tissues with inducible lentiviral particles to express ING proteins. Proliferation was assessed by H3S10phos immunohistochemistry (IHC). The expression of ING3 was assessed by IHC on a human prostate cancer tissue microarray (TMA). Gene expression was measured by DNA microarray and validated by real-time qPCR. RESULTS: We found that ING3 stimulates cellular proliferation in ex vivo tissues, suggesting that ING3 could be oncogenic. Indeed, ING3 overexpression transformed normal human dermal fibroblasts. We observed elevated levels of ING3 in prostate cancer samples, which correlated with poorer patient survival. Consistent with an oncogenic role, gene-silencing experiments revealed that ING3 is required for the proliferation of breast, ovarian, and prostate cancer cells. Finally, ING3 controls the expression of an intricate network of cell cycle genes by associating with chromatin modifiers and the H3K4me3 mark at transcriptional start sites. CONCLUSIONS: Our investigations create a shift in the prevailing view that ING proteins are tumour suppressors and redefine ING3 as an oncoprotein.
Assuntos
Transformação Celular Neoplásica/genética , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Hiperplasia Prostática/genética , Neoplasias da Próstata/genética , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismo , Ciclo Celular , Linhagem Celular , Proliferação de Células , Transformação Celular Neoplásica/metabolismo , Progressão da Doença , Perfilação da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Humanos , Lentivirus/genética , Masculino , Análise de Sequência com Séries de Oligonucleotídeos , Hiperplasia Prostática/metabolismo , Neoplasias da Próstata/metabolismo , Análise Serial de Tecidos , Transdução Genética , Regulação para CimaRESUMO
Although histone post-translational modifications play a paramount role in controlling access to genetic information, our understanding of the precise mechanisms regulating chromatin signaling remains superficial. For instance, histone H3 trimethylated on lysine 9 (H3K9(me3)) favors the association of chromodomain proteins such as heterochromatin protein 1α (HP1α) with chromatin. However, HP1α and other such chromatin proteins are not covering all specific histone marks at all times. Thus, how are these reader-histone interactions regulated? We propose tyrosine phosphorylation within the aromatic cage of histone mark readers as a molecular switch that can either turn ON or OFF and even alter the specificity of reader-histone interactions. We have identified tyrosine phosphorylation events on the chromatin proteins HP1α and M-phase phosphoprotein 8 that regulate their association with methylated histones in vitro (synthetic peptides, calf thymus purified histones, and nucleosomes), but also in cells, thus controlling access to genetic information.