The MAPK/ERK signaling pathway is an essential regulator of numerous cell processes that are crucial for normal development as well as cancer progression. While much is known regarding MAPK/ERK signal conveyance from the cell membrane to the nucleus, the transcriptional and epigenetic mechanisms that govern gene expression downstream of MAPK signaling are not fully elucidated. This study employed an integrated epigenome analysis approach to interrogate the effects of MAPK/ERK pathway inhibition on the global transcriptome, the active chromatin landscape, and protein–DNA interactions in 501mel melanoma cells. Treatment of these cells with the small-molecule MEK inhibitor AZD6244 induces hyperpigmentation, widespread gene expression changes including alteration of genes linked to pigmentation, and extensive epigenomic reprogramming of transcriptionally distinct regulatory regions associated with the active chromatin mark H3K27ac. Regulatory regions with differentially acetylated H3K27ac regions following AZD6244 treatment are enriched in transcription factor binding motifs of ETV/ETS and ATF family members as well as the lineage-determining factors MITF and SOX10. H3K27ac-dense enhancer clusters known as super-enhancers show similar transcription factor motif enrichment, and furthermore, these super-enhancers are associated with genes encoding MITF, SOX10, and ETV/ETS proteins. Along with genome-wide resetting of the active enhancer landscape, MEK inhibition also results in widespread SOX10 recruitment throughout the genome, including increased SOX10 binding density at H3K27ac-marked enhancers. Importantly, these MEK inhibitor-responsive enhancers marked by H3K27ac and occupied by SOX10 are located near melanocyte lineage-specific and pigmentation genes and overlap numerous human SNPs associated with pigmentation and melanoma phenotypes, highlighting the variants located within these regions for prioritization in future studies. These results reveal the epigenetic reprogramming underlying the re-activation of melanocyte pigmentation and developmental transcriptional programs in 501mel cells in response to MEK inhibition and suggest extensive involvement of a MEK-SOX10 axis in the regulation of these processes. The dynamic chromatin changes identified here provide a rich genomic resource for further analyses of the molecular mechanisms governing the MAPK pathway in pigmentation- and melanocyte-associated diseases.

中文翻译：

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MEK抑制重塑了活跃的染色质景观，并在BRAF（V600E）突变型黑色素瘤细胞中诱导了SOX10基因组募集。

MAPK / ERK信号通路是众多细胞过程的重要调节剂，这些过程对于正常发育以及癌症进展至关重要。尽管有关从细胞膜到细胞核的MAPK / ERK信号传递的已知信息很多，但尚未完全阐明控制MAPK信号下游基因表达的转录和表观遗传机制。这项研究采用了整合的表观基因组分析方法，研究了501mel黑色素瘤细胞中MAPK / ERK途径抑制对整体转录组，活性染色质分布以及蛋白质-DNA相互作用的影响。用小分子MEK抑制剂AZD6244处理这些细胞会诱导色素沉着，广泛的基因表达变化，包括与色素沉着相关的基因改变，以及与活性染色质标记H3K27ac相关的转录独特调控区的广泛表观基因组重编程。AZD6244处理后，具有差异乙酰化H3K27ac区域的调节区富含ETV / ETS和ATF家族成员的转录因子结合基序，以及谱系决定因子MITF和SOX10。H3K27ac密集增强子簇称为超级增强子，显示出相似的转录因子基序富集，此外，这些超级增强子与编码MITF，SOX10和ETV / ETS蛋白的基因相关。除了全基因组范围内的活性增强子景观重置之外，MEK抑制还导致整个基因组中广泛的SOX10募集，包括H3K27ac标记的增强子上SOX10结合密度的增加。重要的，这些以H3K27ac标记并被SOX10占据的MEK抑制剂应答增强剂位于黑素细胞谱系特异性和色素沉着基因附近，并且与许多与色素沉着和黑色素瘤表型有关的人类SNP重叠，突出了位于这些区域内的变异体，以便在以后的研究中进行优先排序。这些结果揭示了响应MEK抑制作用而对501mel细胞中黑色素细胞色素沉着的重新激活和发育转录程序背后的表观遗传重编程，并暗示了MEK-SOX10轴广泛参与了这些过程的调节。此处确定的动态染色质变化提供了丰富的基因组资源，可用于进一步分析控制色素沉着和黑素细胞相关疾病中MAPK途径的分子机制。