RESUMO
Oxidation of histone H3 at lysine 4 (H3K4ox) is catalyzed by lysyl oxidase homolog 2 (LOXL2). This histone modification is enriched in heterochromatin in triple-negative breast cancer (TNBC) cells and has been linked to the maintenance of compacted chromatin. However, the molecular mechanism underlying this maintenance is still unknown. Here, we show that LOXL2 interacts with RuvB-Like 1 (RUVBL1), RuvB-Like 2 (RUVBL2), Actin-like protein 6A (ACTL6A), and DNA methyltransferase 1associated protein 1 (DMAP1), a complex involved in the incorporation of the histone variant H2A.Z. Our experiments indicate that this interaction and the active form of RUVBL2 are required to maintain LOXL2-dependent chromatin compaction. Genome-wide experiments showed that H2A.Z, RUVBL2, and H3K4ox colocalize in heterochromatin regions. In the absence of LOXL2 or RUVBL2, global levels of the heterochromatin histone mark H3K9me3 were strongly reduced, and the ATAC-seq signal in the H3K9me3 regions was increased. Finally, we observed that the interplay between these series of events is required to maintain H3K4ox-enriched heterochromatin regions, which in turn is key for maintaining the oncogenic properties of the TNBC cell line tested (MDA-MB-231).
Assuntos
Aminoácido Oxirredutases , Heterocromatina , Histonas , Neoplasias de Mama Triplo Negativas , Neoplasias de Mama Triplo Negativas/genética , Neoplasias de Mama Triplo Negativas/patologia , Neoplasias de Mama Triplo Negativas/metabolismo , Humanos , Aminoácido Oxirredutases/genética , Aminoácido Oxirredutases/metabolismo , Histonas/metabolismo , Histonas/genética , Feminino , Heterocromatina/metabolismo , Heterocromatina/genética , Linhagem Celular Tumoral , Cromatina/metabolismo , Cromatina/genética , Regulação Neoplásica da Expressão Gênica , DNA Helicases/genética , DNA Helicases/metabolismoRESUMO
Triple-negative breast cancer (TNBC) often develops resistance to single-agent treatment, which can be circumvented using targeted combinatorial approaches. Here, we demonstrate that the simultaneous inhibition of LOXL2 and BRD4 synergistically limits TNBC proliferation in vitro and in vivo. Mechanistically, LOXL2 interacts in the nucleus with the short isoform of BRD4 (BRD4S), MED1, and the cell cycle transcriptional regulator B-MyB. These interactions sustain the formation of BRD4 and MED1 nuclear transcriptional foci and control cell cycle progression at the gene expression level. The pharmacological co-inhibition of LOXL2 and BRD4 reduces BRD4 nuclear foci, BRD4-MED1 colocalization, and the transcription of cell cycle genes, thus suppressing TNBC cell proliferation. Targeting the interaction between BRD4S and LOXL2 could be a starting point for the development of new anticancer strategies for the treatment of TNBC.
Assuntos
Fatores de Transcrição , Neoplasias de Mama Triplo Negativas , Humanos , Aminoácido Oxirredutases/genética , Aminoácido Oxirredutases/metabolismo , Proteínas que Contêm Bromodomínio , Ciclo Celular , Proteínas de Ciclo Celular/metabolismo , Linhagem Celular Tumoral , Proliferação de Células/genética , Regulação Neoplásica da Expressão Gênica , Subunidade 1 do Complexo Mediador/genética , Subunidade 1 do Complexo Mediador/metabolismo , Proteínas Nucleares/genética , Fatores de Transcrição/metabolismo , Neoplasias de Mama Triplo Negativas/genética , Neoplasias de Mama Triplo Negativas/tratamento farmacológico , Neoplasias de Mama Triplo Negativas/metabolismo , AnimaisRESUMO
Histone H1 has seven variants in human somatic cells and contributes to chromatin compaction and transcriptional regulation. Knock-down (KD) of each H1 variant in breast cancer cells results in altered gene expression and proliferation differently in a variant specific manner with H1.2 and H1.4 KDs being most deleterious. Here we show combined depletion of H1.2 and H1.4 has a strong deleterious effect resulting in a strong interferon (IFN) response, as evidenced by an up-regulation of many IFN-stimulated genes (ISGs) not seen in individual nor in other combinations of H1 variant KDs. Although H1 participates to repress ISG promoters, IFN activation upon H1.2 and H1.4 KD is mainly generated through the activation of the IFN response by cytosolic nucleic acid receptors and IFN synthesis, and without changes in histone modifications at induced ISG promoters. H1.2 and H1.4 co-KD also promotes the appearance of accessibility sites genome wide and, particularly, at satellites and other repeats. The IFN response may be triggered by the expression of noncoding RNA generated from heterochromatic repeats or endogenous retroviruses upon H1 KD. In conclusion, redundant H1-mediated silencing of heterochromatin is important to maintain cell homeostasis and to avoid an unspecific IFN response.
Assuntos
Neoplasias da Mama/genética , Proliferação de Células/genética , Heterocromatina/metabolismo , Histonas/genética , Interferons/metabolismo , Ativação Transcricional/genética , Linhagem Celular Tumoral , Montagem e Desmontagem da Cromatina/genética , Feminino , Regulação da Expressão Gênica/genética , Células HeLa , Humanos , Células MCF-7 , Interferência de RNA , RNA Interferente Pequeno/genética , Transcrição GênicaRESUMO
Methylation of histone H3 lysine 4 is linked to active transcription and can be removed by LSD1 or the JmjC domain-containing proteins by amino-oxidation or hydroxylation, respectively. Here we describe that its deamination can be catalyzed by lysyl oxidase-like 2 protein (LOXL2), presenting an unconventional chemical mechanism for H3K4 modification. Infrared spectroscopy and mass spectrometry analyses demonstrated that recombinant LOXL2 specifically deaminates trimethylated H3K4. Moreover, by regulating H3K4me3 deamination, LOXL2 activity is linked with the transcriptional control of the CDH1 gene. These results reveal the existence of further H3 modification as well as a novel mechanism for H3K4me3 demethylation. DATABASE: The GEO accession number for the data referred to this paper is GSE35600.