Analysis of long and short enhancers in melanoma cell states
Abstract
Understanding how enhancers drive cell type specificity and efficiently identifying them is essential for the development of innovative therapeutic strategies. In melanoma, the melanocytic (MEL) and the mesenchymal-like (MES) states present themselves with different responses to therapy, making the identification of specific enhancers highly relevant. Using massively parallel reporter assays (MPRA) in a panel of patient-derived melanoma lines (MM lines), we set to identify and decipher melanoma enhancers by first focusing on regions with state specific H3K27 acetylation close to differentially expressed genes. An in-depth evaluation of those regions was then pursued by investigating the activity of overlapping ATAC-seq peaks along with a full tiling of the acetylated regions with 190 bp sequences. Activity was observed in more than 60% of the selected regions and we were able to precisely locate the active enhancers within ATAC-seq peaks. Comparison of sequence content with activity, using the deep learning model DeepMEL2, revealed that AP-1 alone is responsible for the MES enhancer activity. In contrast, SOX10 and MITF both influence MEL enhancer function with SOX10 being required to achieve high levels of activity. Overall, our MPRAs shed light on the relationship between long and short sequences in terms of their sequence content, enhancer activity, and specificity across melanoma cell states.
Data availability
Sequencing data have been deposited in GEO under accession codes GSE180879.Enhancer activity tables for each library is provided as source data.Scripts used for enhancer - barcode assignment, read processing and activity measurement and analysis are provided in the Scripts directory.
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Analysis of long and short enhancers in melanoma cell statesNCBI Gene Expression Omnibus, GSE180879.
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TFAP2A ChIP-seq in human primary melanocytesNCBI Gene Expression Omnibus, GSE67555.
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Decoding the regulatory landscape of melanoma reveals TEADS as regulators of the invasive cell state.NCBI Gene Expression Omnibus, GSE60666.
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cisTopic: cis-regulatory topic modelling on single-cell ATAC-seq dataNCBI Gene Expression Omnibus, GSE114557.
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Cross-species analysis of melanoma enhancer logic using deep learningNCBI Gene Expression Omnibus, GSE142238.
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Single-cell analysis of gene expression variation and phenotype switching in melanomaNCBI Gene Expression Omnibus, GSE134432.
Article and author information
Author details
Funding
H2020 European Research Council (724226_cis-CONTROL)
- Stein Aerts
KU Leuven (C14/18/092)
- Stein Aerts
Fonds Wetenschappelijk Onderzoek (1S03317N)
- Liesbeth Minnoye
Fonds Wetenschappelijk Onderzoek (12J6916N)
- Jonas Demeulemeester
Kom op tegen Kanker
- Jasper Wouters
H2020 European Research Council (724226_cis-CONTROL)
- David Mauduit
H2020 European Research Council (724226_cis-CONTROL)
- Valerie Christiaens
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2021, Mauduit et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Further reading
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- Chromosomes and Gene Expression
- Developmental Biology
The male-specific lethal complex (MSL), which consists of five proteins and two non-coding roX RNAs, is involved in the transcriptional enhancement of X-linked genes to compensate for the sex chromosome monosomy in Drosophila XY males compared with XX females. The MSL1 and MSL2 proteins form the heterotetrameric core of the MSL complex and are critical for the specific recruitment of the complex to the high-affinity ‘entry’ sites (HAS) on the X chromosome. In this study, we demonstrated that the N-terminal region of MSL1 is critical for stability and functions of MSL1. Amino acid deletions and substitutions in the N-terminal region of MSL1 strongly affect both the interaction with roX2 RNA and the MSL complex binding to HAS on the X chromosome. In particular, substitution of the conserved N-terminal amino-acids 3–7 in MSL1 (MSL1GS) affects male viability similar to the inactivation of genes encoding roX RNAs. In addition, MSL1GS binds to promoters such as MSL1WT but does not co-bind with MSL2 and MSL3 to X chromosomal HAS. However, overexpression of MSL2 partially restores the dosage compensation. Thus, the interaction of MSL1 with roX RNA is critical for the efficient assembly of the MSL complex on HAS of the male X chromosome.
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- Chromosomes and Gene Expression
- Genetics and Genomics
The enhancer-promoter looping model, in which enhancers activate their target genes via physical contact, has long dominated the field of gene regulation. However, the ubiquity of this model has been questioned due to evidence of alternative mechanisms and the lack of its systematic validation, primarily owing to the absence of suitable experimental techniques. In this study, we present a new MNase-based proximity ligation method called MChIP-C, allowing for the measurement of protein-mediated chromatin interactions at single-nucleosome resolution on a genome-wide scale. By applying MChIP-C to study H3K4me3 promoter-centered interactions in K562 cells, we found that it had greatly improved resolution and sensitivity compared to restriction endonuclease-based C-methods. This allowed us to identify EP300 histone acetyltransferase and the SWI/SNF remodeling complex as potential candidates for establishing and/or maintaining enhancer-promoter interactions. Finally, leveraging data from published CRISPRi screens, we found that most functionally verified enhancers do physically interact with their cognate promoters, supporting the enhancer-promoter looping model.