Genomic transcription factor binding site selection is edited by the chromatin remodeling factor CHD4.

Biologically precise enhancer licensing by lineage-determining transcription factors enables activation of transcripts appropriate to biological demand and prevents deleterious gene activation. This essential process is challenged by the millions of matches to most transcription factor binding motifs present in many eukaryotic genomes, leading to questions about how transcription factors achieve the exquisite specificity required. The importance of chromatin remodeling factors to enhancer activation is highlighted by their frequent mutation in developmental disorders and in cancer. Here, we determine the roles of CHD4 in enhancer licensing and maintenance in breast cancer cells and during cellular reprogramming. In unchallenged basal breast cancer cells, CHD4 modulates chromatin accessibility. Its depletion leads to redistribution of transcription factors to previously unoccupied sites. During cellular reprogramming induced by the pioneer factor GATA3, CHD4 activity is necessary to prevent inappropriate chromatin opening. Mechanistically, CHD4 promotes nucleosome positioning over GATA3 binding motifs to compete with transcription factor-DNA interaction. We propose that CHD4 acts as a chromatin proof-reading enzyme that prevents unnecessary gene expression by editing chromatin binding activities of transcription factors.

Identification of neoblast- and regeneration-specific miRNAs in the planarian Schmidtea mediterranea.

In recent years, the planarian Schmidtea mediterranea has emerged as a tractable model system to study stem cell biology and regeneration. MicroRNAs are small RNA species that control gene expression by modulating translational repression and mRNA stability and have been implicated in the regulation of various cellular processes. Though recent studies have identified several miRNAs in S. mediterranea, their expression in neoblast subpopulations and during regeneration has not been examined. Here, we identify several miRNAs whose expression is enriched in different neoblast subpopulations and in regenerating tissue at different time points in S. mediterranea. Some of these miRNAs were enriched within 3 h post-amputation and may, therefore, play a role in wound healing and/or neoblast migration. Our results also revealed miRNAs, such as sme-miR-2d-3p and the sme-miR-124 family, whose expression is enriched in the cephalic ganglia, are also expressed in the brain primordium during CNS regeneration. These results provide new insight into the potential biological functions of miRNAs in neoblasts and regeneration in planarians.

Deep sequencing reveals unique small RNA repertoire that is regulated during head regeneration in Hydra magnipapillata.

Small non-coding RNAs such as miRNAs, piRNAs and endo-siRNAs fine-tune gene expression through post-transcriptional regulation, modulating important processes in development, differentiation, homeostasis and regeneration. Using deep sequencing, we have profiled small non-coding RNAs in Hydra magnipapillata and investigated changes in small RNA expression pattern during head regeneration. Our results reveal a unique repertoire of small RNAs in hydra. We have identified 126 miRNA loci; 123 of these miRNAs are unique to hydra. Less than 50% are conserved across two different strains of Hydra vulgaris tested in this study, indicating a highly diverse nature of hydra miRNAs in contrast to bilaterian miRNAs. We also identified siRNAs derived from precursors with perfect stem-loop structure and that arise from inverted repeats. piRNAs were the most abundant small RNAs in hydra, mapping to transposable elements, the annotated transcriptome and unique non-coding regions on the genome. piRNAs that map to transposable elements and the annotated transcriptome display a ping-pong signature. Further, we have identified several miRNAs and piRNAs whose expression is regulated during hydra head regeneration. Our study defines different classes of small RNAs in this cnidarian model system, which may play a role in orchestrating gene expression essential for hydra regeneration.

Impact of renal cell carcinoma molecular subtypes on immunotherapy and targeted therapy outcomes.

Saliby et al. show that a machine learning approach can accurately classify clear cell renal cell carcinoma (RCC) into distinct molecular subtypes using transcriptomic data. When applied to tumors biospecimens from the JAVELIN Renal 101 (JR101) trial, a benefit is observed with immune checkpoint inhibitor (ICI)-based therapy across all molecular subtypes.

Genomic transcription factor binding site selection is edited by the chromatin remodeling factor CHD4.

Biologically precise enhancer licensing by lineage-determining transcription factors enables activation of transcripts appropriate to biological demand and prevents deleterious gene activation. This essential process is challenged by the millions of matches to most transcription factor binding motifs present in many eukaryotic genomes, leading to questions about how transcription factors achieve the exquisite specificity required. The importance of chromatin remodeling factors to enhancer activation is highlighted by their frequent mutation in developmental disorders and in cancer. Here we determine the roles of CHD4 to enhancer licensing and maintenance in breast cancer cells and during cellular reprogramming. In unchallenged basal breast cancer cells, CHD4 modulates chromatin accessibility at transcription factor binding sites; its depletion leads to altered motif scanning and redistribution of transcription factors to sites not previously occupied. During GATA3-mediated cellular reprogramming, CHD4 activity is necessary to prevent inappropriate chromatin opening and enhancer licensing. Mechanistically, CHD4 competes with transcription factor-DNA interaction by promoting nucleosome positioning over binding motifs. We propose that CHD4 acts as a chromatin proof-reading enzyme that prevents inappropriate gene expression by editing binding site selection by transcription factors.

GATA3 Truncation Mutants Alter EMT Related Gene Expression via Partial Motif Recognition in Luminal Breast Cancer Cells.

GATA3 is known to be one of the most frequently mutated genes in breast cancer. More than 10% of breast tumors carry mutations in this gene. However, the functional consequence of GATA3 mutations is still largely unknown. Clinical data suggest that different types of GATA3 mutations may have distinct roles in breast cancer characterization. In this study, we have established three luminal breast cancer cell lines that stably express different truncation mutants (X308 splice site deletion, C321 frameshift, and A333 frameshift mutants) found in breast cancer patients. Transcriptome analysis identified common and distinct gene expression patterns in these GATA3 mutant cell lines. In particular, the impacts on epithelial-to-mesenchymal transition (EMT) related genes are similar across these mutant cell lines. Chromatin localization of the mutants is highly overlapped and exhibits non-canonical motif enrichment. Interestingly, the A333 frameshift mutant expressed cells displayed the most significant impact on the GATA3 binding compared to X308 splice site deletion and C321fs mutants expressed cells. Our results suggest the common and different roles of GATA3 truncation mutations during luminal breast cancer development.

Correction: The novel microRNAs hsa-miR-nov7 and hsa-miR-nov3 are over-expressed in locally advanced breast cancer.

[This corrects the article DOI: 10.1371/journal.pone.0225357.].

The novel microRNAs hsa-miR-nov7 and hsa-miR-nov3 are over-expressed in locally advanced breast cancer.

miRNAs are an important class of small non-coding RNAs, which play a versatile role in gene regulation at the post-transcriptional level. Expression of miRNAs is often deregulated in human cancers. We analyzed small RNA massive parallel sequencing data from 50 locally advanced breast cancers aiming to identify novel breast cancer related miRNAs. We successfully predicted 10 novel miRNAs, out of which 2 (hsa-miR-nov3 and hsa-miR-nov7) were recurrent. Applying high sensitivity qPCR, we detected these two microRNAs in 206 and 214 out of 223 patients in the study from which the initial cohort of 50 samples were drawn. We found hsa-miR-nov3 and hsa-miR-nov7 both to be overexpressed in tumor versus normal breast tissue in a separate set of 13 patients (p = 0.009 and p = 0.016, respectively) from whom both tumor tissue and normal tissue were available. We observed hsa-miR-nov3 to be expressed at higher levels in ER-positive compared to ER-negative tumors (p = 0.037). Further stratifications revealed particularly low levels in the her2-like and basal-like cancers compared to other subtypes (p = 0.009 and 0.040, respectively). We predicted target genes for the 2 microRNAs and identified inversely correlated genes in mRNA expression array data available from 203 out of the 223 patients. Applying the KEGG and GO annotations to target genes revealed pathways essential to cell development, communication and homeostasis. Although a weak association between high expression levels of hsa-miR-nov7 and poor survival was observed, this did not reach statistical significance. hsa-miR-nov3 expression levels had no impact on patient survival.

Assessment of tumor suppressor promoter methylation in healthy individuals.

BACKGROUND: The number of tumor suppressor genes for which germline mutations have been linked to cancer risk is steadily increasing. However, while recent reports have linked constitutional normal tissue promoter methylation of BRCA1 and MLH1 to ovarian and colon cancer risk, the role of epigenetic alterations as cancer risk factors remains largely unknown, presenting an important area for future research. Currently, we lack fast and sensitive methods for assessment of promoter methylation status across known tumor suppressor genes. RESULTS: In this paper, we present a novel NGS-based approach assessing promoter methylation status across a large panel of defined tumor suppressor genes to base-pair resolution. The method omits the limitations related to commonly used array-approaches. Our panel includes 565 target regions covering the promoters of 283 defined tumor suppressors, selected by pre-specified criteria, and was applied for rapid targeted methylation-specific NGS. The feasibility of the method was assessed by analyzing normal tissue DNA (white blood cells, WBC) samples from 34 healthy postmenopausal women and by performing preliminary assessment of the methylation landscape of tumor suppressors in these individuals. The mean target coverage was 189.6x providing a sensitivity of 0.53%, sufficient for promoter methylation assessment of low-level methylated genes like BRCA1. Within this limited test-set, we detected 206 regions located in the promoters of 149 genes to be differentially methylated (hyper- or hypo-) at > 99% confidence level. Seven target regions in gene promoters (CIITA, RASSF1, CHN1, PDCD1LG2, GSTP1, XPA, and ZNF668) were found to be hyper-methylated in a minority of individuals, with a > 20 percent point difference in mean methylation across the region between individuals. In an exploratory hierarchical clustering analysis, we found that the individuals analyzed may be grouped into two main groups based on their WBC methylation profile across the 283 tumor suppressor gene promoters. CONCLUSIONS: Methylation-specific NGS of our tumor suppressor panel, with detailed assessment of differential methylation in healthy individuals, presents a feasible method for identification of novel epigenetic risk factors for cancer.

Genome-Wide Analysis of Polyadenylation Events in Schmidtea mediterranea.

In eukaryotes, 3' untranslated regions (UTRs) play important roles in regulating posttranscriptional gene expression. The 3'UTR is defined by regulated cleavage/polyadenylation of the pre-mRNA. The advent of next-generation sequencing technology has now enabled us to identify these events on a genome-wide scale. In this study, we used poly(A)-position profiling by sequencing (3P-Seq) to capture all poly(A) sites across the genome of the freshwater planarian, Schmidtea mediterranea, an ideal model system for exploring the process of regeneration and stem cell function. We identified the 3'UTRs for ∼14,000 transcripts and thus improved the existing gene annotations. We found 97 transcripts, which are polyadenylated within an internal exon, resulting in the shrinking of the ORF and loss of a predicted protein domain. Around 40% of the transcripts in planaria were alternatively polyadenylated (ApA), resulting either in an altered 3'UTR or a change in coding sequence. We identified specific ApA transcript isoforms that were subjected to miRNA mediated gene regulation using degradome sequencing. In this study, we also confirmed a tissue-specific expression pattern for alternate polyadenylated transcripts. The insights from this study highlight the potential role of ApA in regulating the gene expression essential for planarian regeneration.