Antisense RNAs and epigenetic regulation

DNAJC9 expression in basal-like and luminal A breast cancer subtypes predicts worse survival

BACKGROUND

This study aimed to analyze the role of genetic/epigenetic alterations and the prognostic value of the DNAJC9 gene in breast cancer.

MATERIALS AND METHODS

RT-PCR and Q-RT-PCR methods are used to examine DNAJC9 expression in breast cell lines. Survival ratios of breast cancer patients were evaluated by using bc-GenExMiner. Combined bisulfite restriction analysis and UALCAN in-silico tool were used to assess the methylation level of the DNAJC9 promoter. Mutations were searched with the help of Sanger Cosmic database and direct sequencing.

RESULTS

DNAJC9 mRNA expression is significantly higher in basal-like, HER2-Enriched (HER2-E), luminal A and luminal B breast cancer subtypes compared to normal breast-like samples based on DNA microarray datasets (P < 0.001). Similar results were obtained in RNA-seq datasets, except for the luminal A breast cancer subtype (P > 0.1). We did not find any mutation at the core promoter region of DNAJC9 in breast cancer and normal cell lines. Mutations of DNAJC9 are infrequent in clinical samples (<%1). DNAJC9 promoter region is hypomethylated in tumor and normal samples. DNAJC9 expression is unfavorable for survival in basal-like and luminal A breast cancer subtypes.

CONCLUSIONS

Mutations or promoter hypomethylation do not appear to have a role in high DNAJC9 gene expression in breast cancer. DNAJC9 expression could be suggested as a novel biomarker in basal-like and luminal A breast cancer subtypes.

Long noncoding RNA BMPR1B-AS1 facilitates endometrial cancer cell proliferation and metastasis by sponging miR-7-2-3p to modulate the DCLK1/Akt/NF-κB pathway

Endometrial carcinoma (EC) originates from the endometrium and is one of the most common tumors in female patients, and its incidence has continued to increase in recent decades. LncRNAs are involved in the pathogenesis and metastasis of a variety of malignant tumors, which indicates that lncRNAs can be used as tumor diagnostic markers and potential therapeutic targets. In this study, we analyzed the RNA transcripts of EC cells from The Cancer Genome Atlas (TCGA) and first reported a novel lncRNA, BMPR1B-AS1, that was more highly expressed in endometrial cancer tissues than in adjacent tissues, and BMPR1B-AS1 could promote endometrial cancer cell proliferation and metastasis. Bioinformatics prediction and experimental results both suggested that BMPR1B-AS1 could modulate the malignant behaviors of endometrial cancer cell lines by sponging miR-7-2-3p to modulate DCLK1, and a DCLK1 inhibitor blocked the activation of the PI3K/Akt/NF-κB signaling pathway. Collectively, this study suggests that the BMPR1B-AS1/miR-7-2-3p/DCLK1 axis contributes to the proliferation and metastasis of endometrial cancer cells via the PI3K/Akt/NF-κB pathway.

Long non-coding RNA ILF3-AS1 facilitates hepatocellular carcinoma progression by stabilizing ILF3 mRNA in an m6A-dependent manner

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. Increasing evidences have demonstrated that ILF3 antisense RNA 1 (ILF3-AS1) acts as an oncogenic long noncoding RNA (lncRNA) in several types of human cancers. However, the expression pattern, functional role and underlying mechanism of ILF3-AS1 in HCC remains largely unclear. Here, we found that ILF3-AS1 expression was significantly elevated in HCC tissues and also associated with prognosis of patients with HCC. Functional assays demonstrated that knockdown of ILF3-AS1 expression resulted in the suppression of proliferation, migration and invasion in HCC cells, whereas overexpression of ILF3-AS1 exerted opposite effects. Additionally, knockdown of IFL3-AS1 attenuated HCC tumorigenesis and metastasis in vivo. Mechanistically, ILF3-AS1 associated with ILF3 mRNA and inhibited its degradation. ILF3-AS1 increased ILF3 m⁶A level via recruiting N⁶-methyladenosine (m⁶A) RNA methyltransferase METTL3. Moreover, IFL3-AS1 enhanced the interaction between ILF3 mRNA and m⁶A reader IGF2BP1. Overall, our study revealed the function and mechanism of ILF3-AS1 in the malignant phenotypes of HCC cells, which provides a novel therapeutic target for HCC.

Natural antisense transcripts in the biological hallmarks of cancer: powerful regulators hidden in the dark

Natural antisense transcripts (NATs), which are transcribed from opposite strands of DNA with partial or complete overlap, affect multiple stages of gene expression, from epigenetic to post-translational modifications. NATs are dysregulated in various types of cancer, and an increasing number of studies focusing on NATs as pivotal regulators of the hallmarks of cancer and as promising candidates for cancer therapy are just beginning to unravel the mystery. Here, we summarize the existing knowledge on NATs to highlight their underlying mechanisms of functions in cancer biology, discuss their potential roles in therapeutic application, and explore future research directions.

OverGeneDB: a database of 5' end protein coding overlapping genes in human and mouse genomes

Gene overlap plays various regulatory functions on transcriptional and post-transcriptional levels. Most current studies focus on protein-coding genes overlapping with non-protein-coding counterparts, the so called natural antisense transcripts. Considerably less is known about the role of gene overlap in the case of two protein-coding genes. Here, we provide OverGeneDB, a database of human and mouse 5′ end protein-coding overlapping genes. The database contains 582 human and 113 mouse gene pairs that are transcribed using overlapping promoters in at least one analyzed library. Gene pairs were identified based on the analysis of the transcription start site (TSS) coordinates in 73 human and 10 mouse organs, tissues and cell lines. Beside TSS data, resources for 26 human lung adenocarcinoma cell lines also contain RNA-Seq and ChIP-Seq data for seven histone modifications and RNA Polymerase II activity. The collected data revealed that the overlap region is rarely conserved between the studied species and tissues. In ∼50% of the overlapping genes, transcription started explicitly in the overlap regions. In the remaining half of overlapping genes, transcription was initiated both from overlapping and non-overlapping TSSs. OverGeneDB is accessible at http://overgenedb.amu.edu.pl.

Prenatal adverse environment is associated with epigenetic age deceleration at birth and hypomethylation at the hypoxia-responsive EP300 gene

BACKGROUND

Obstetric complications have long been retrospectively associated with a wide range of short- and long-term health consequences, including neurodevelopmental alterations such as those observed in schizophrenia and other psychiatric disorders. However, prospective studies assessing fetal well-being during pregnancy tend to focus on perinatal complications as the final outcome of interest, while there is a scarcity of postnatal follow-up studies. In this study, the cerebroplacental ratio (CPR), a hemodynamic parameter reflecting fetal adaptation to hypoxic conditions, was analyzed in a sample of monozygotic monochorionic twins (60 subjects), part of them with prenatal complications, with regard to (i) epigenetic age acceleration, and (ii) DNA methylation at genes included in the polygenic risk score (PRS) for schizophrenia, and highly expressed in placental tissue.

RESULTS

Decreased CPR measured during the third trimester was associated with epigenetic age deceleration (β = 0.21, t = 3.362, p = 0.002). Exploration of DNA methylation at placentally expressed genes of the PRS for schizophrenia revealed methylation at cg06793497 (EP300 gene) to be associated with CPR (β = 0.021, t = 4.385; p = 0.00008, FDR-adjusted p = 0.11). This association was reinforced by means of an intrapair analysis in monozygotic twins discordant for prenatal suffering (β = 0.027, t = 3.924, p = 0.001).

CONCLUSIONS

Prenatal adverse environment during the third trimester of pregnancy is associated with both (i) developmental immaturity in terms of epigenetic age, and (ii) decreased CpG-specific methylation in a gene involved in hypoxia response and schizophrenia genetic liability.

Identification of a novel antisense RNA that regulates growth hormone receptor expression in chickens

Natural antisense transcripts (NATs) are widely present in mammalian genomes and act as pivotal regulator molecules of gene expression. However, studies on NATs in the chicken are relatively rare. We identified a novel antisense transcript in the chicken, designated GHR-AS-EST, transcribed from the growth hormone receptor (GHR) locus, which encodes a well-known regulatory molecule of muscle development and fat deposition. GHR-AS-EST is predominantly expressed in the chicken liver and muscle tissues. GHR-AS-EST sequence conservation among vertebrates is weak. GHR-AS-EST forms an RNA-RNA duplex with GHBP to increase its stability, and regulates the expression of GHR sense transcripts at both the mRNA and protein levels. Further, GHR-AS-EST promotes cell proliferation by stimulating the expression of signaling factors in the JAK2/STAT pathway, and contributes to fat deposition via downregulating the expression of signaling factors in the JAK2/SOCS pathway in LMH hepatocellular carcinoma cells. We expect that the discovery of a NAT for a regulatory gene associated with cell proliferation and lipolysis will further our understanding of the molecular regulation of both muscle development and fat deposition.

Conserved expression of natural antisense transcripts in mammals

Background

Recent studies had found thousands of natural antisense transcripts originating from the same genomic loci of protein coding genes but from the opposite strand. It is unclear whether the majority of antisense transcripts are functional or merely transcriptional noise.

Results

Using the Affymetrix Exon array with a modified cDNA synthesis protocol that enables genome-wide detection of antisense transcription, we conducted large-scale expression analysis of antisense transcripts in nine corresponding tissues from human, mouse and rat. We detected thousands of antisense transcripts, some of which show tissue-specific expression that could be subjected to further study for their potential function in the corresponding tissues/organs. The expression patterns of many antisense transcripts are conserved across species, suggesting selective pressure on these transcripts. When compared to protein-coding genes, antisense transcripts show a lesser degree of expression conservation. We also found a positive correlation between the sense and antisense expression across tissues.

Conclusion

Our results suggest that natural antisense transcripts are subjected to selective pressure but to a lesser degree compared to sense transcripts in mammals.