Ovarian cancer proliferation and apoptosis are regulated by human transfer RNA methyltransferase 9-likevia LIN9

Expanded tRNA methyltransferase family member TRMT9B regulates synaptic growth and function

Nervous system function rests on the formation of functional synapses between neurons. We have identified TRMT9B as a new regulator of synapse formation and function in Drosophila. TRMT9B has been studied for its role as a tumor suppressor and is one of two metazoan homologs of yeast tRNA methyltransferase 9 (Trm9), which methylates tRNA wobble uridines. Whereas Trm9 homolog ALKBH8 is ubiquitously expressed, TRMT9B is enriched in the nervous system. However, in the absence of animal models, TRMT9B's role in the nervous system has remained unstudied. Here, we generate null alleles of TRMT9B and find it acts postsynaptically to regulate synaptogenesis and promote neurotransmission. Through liquid chromatography-mass spectrometry, we find that ALKBH8 catalyzes canonical tRNA wobble uridine methylation, raising the question of whether TRMT9B is a methyltransferase. Structural modeling studies suggest TRMT9B retains methyltransferase function and, in vivo, disruption of key methyltransferase residues blocks TRMT9B's ability to rescue synaptic overgrowth, but not neurotransmitter release. These findings reveal distinct roles for TRMT9B in the nervous system and highlight the significance of tRNA methyltransferase family diversification in metazoans.

RNA epigenetic modifications in ovarian cancer: The changes, chances, and challenges

Ovarian cancer (OC) is the most common female cancer worldwide. Patients with OC have high mortality because of its complex and poorly understood pathogenesis. RNA epigenetic modifications, such as m6 A, m1 A, and m5 C, are closely associated with the occurrence and development of OC. RNA modifications can affect the stability of mRNA transcripts, nuclear export of RNAs, translation efficiency, and decoding accuracy. However, there are few overviews that summarize the link between m6 A RNA modification and OC. Here, we discuss the molecular and cellular functions of different RNA modifications and how their regulation contributes to the pathogenesis of OC. By improving our understanding of the role of RNA modifications in the etiology of OC, we provide new perspectives for their use in OC diagnosis and treatment. This article is categorized under: RNA Processing > RNA Editing and Modification RNA in Disease and Development > RNA in Disease.

tRNA Modifications and Modifying Enzymes in Disease, the Potential Therapeutic Targets

tRNA is one of the most conserved and abundant RNA species, which plays a key role during protein translation. tRNA molecules are post-transcriptionally modified by tRNA modifying enzymes. Since high-throughput sequencing technology has developed rapidly, tRNA modification types have been discovered in many research fields. In tRNA, numerous types of tRNA modifications and modifying enzymes have been implicated in biological functions and human diseases. In our review, we talk about the relevant biological functions of tRNA modifications, including tRNA stability, protein translation, cell cycle, oxidative stress, and immunity. We also explore how tRNA modifications contribute to the progression of human diseases. Based on previous studies, we discuss some emerging techniques for assessing tRNA modifications to aid in discovering different types of tRNA modifications.

The inhibitory effect of KIAA1456 on the proliferation and metastasis of epithelial ovarian cancer through SSX1 and AKT signaling pathway

Background: KIAA1456 is effective in the inhibition of tumorigenesis. We previously confirmed that KIAA1456 inhibits cell proliferation and metastasis in epithelial ovarian cancer (EOC). In the current study, the specific molecular mechanisms and clinical significance of KIAA1456 underlying the repression of EOC were investigated. Methods: Immunohistochemistry was used to evaluate the protein expression of KIAA1456 and SSX1 in EOC and normal ovarian tissues. The relationship of KIAA1456 and SSX1 with overall survival of patients with EOC was analysed with Kaplan-Meier survival curve and log-rank tests. KIAA1456 was overexpressed and silenced in HO8910PM cells with lentivirus. Anticancer activities of KIAA1456 was tested by CCK8, plate clone formation assay, flow cytometry, wound healing assay and Transwell invasion assay. Xenograft tumour models were used to investigate the effects of KIAA1456 on tumour growth in vivo. Bioinformatics analyses of microarray profiling indicated that SSX1 and the PI3K/AKT were differentially expressed in KIAA1456-overexpressing and control cells. The downstream factors of PI3K/AKT that are related to cell growth and apoptosis. Results: KIAA1456 expression was lower in EOC than in normal ovarian tissues. Its expression negatively correlated with pathological grade. Pearson's correlation analysis showed that KIAA1456 negatively correlated with SSX1 expression. The overexpression of KIAA1456 in HO8910PM cells inhibited proliferation, migration and invasion and promoted apoptosis. The silencing of KIAA1456 resulted in the opposite behaviour. A xenograft tumour experiment showed that KIAA1456 overexpression inhibited tumour growth in vivo. The overexpression of KIAA1456 inhibited SSX1 and AKT phosphorylation in HO8910PM cells, causing the inactivation of the AKT pathway and eventually reducing the expression of PCNA, CyclinD1, MMP9 and Bcl2. The silencing of KIAA1456 resulted in the opposite behaviour. SSX1 overexpression could partially reverse the KIAA1456-induced biological effect. Conclusion: KIAA1456 may serve as a tumour suppressor via the inactivation of SSX1 and the AKT pathway, providing a promising therapeutic target for EOC.

FTSJ1 regulates tRNA 2'-O-methyladenosine modification and suppresses the malignancy of NSCLC via inhibiting DRAM1 expression

Non-small cell lung cancer (NSCLC) is the leading cause of cancer mortality worldwide. The mechanisms underlying NSCLC tumorigenesis are incompletely understood. Transfer RNA (tRNA) modification is emerging as a novel regulatory mechanism for carcinogenesis. However, the role of tRNA modification in NSCLC remains obscure. In this study, HPLC/MS assay was used to quantify tRNA modification levels in NSCLC tissues and cells. tRNA-modifying enzyme genes were identified by comparative genomics and validated by qRT-PCR analysis. The biological functions of tRNA-modifying gene in NSCLC were investigated in vitro and in vivo. The mechanisms of tRNA-modifying gene in NSCLC were explored by RNA-seq, qRT-PCR, and rescue assays. The results showed that a total of 18 types of tRNA modifications and up to seven tRNA-modifying genes were significantly downregulated in NSCLC tumor tissues compared with that in normal tissues, with the 2'-O-methyladenosine (Am) modification displaying the lowest level in tumor tissues. Loss- and gain-of-function assays revealed that the amount of Am in tRNAs was significantly associated with expression levels of FTSJ1, which was also downregulated in NSCLC tissues and cells. Upregulation of FTSJ1 inhibited proliferation, migration, and promoted apoptosis of NSCLC cells in vitro. Silencing of FTSJ1 resulted in the opposite effects. In vivo assay confirmed that overexpression of FTSJ1 significantly suppressed the growth of NSCLC cells. Mechanistically, overexpression of FTSJ1 led to a decreased expression of DRAM1. Whereas knockdown of FTSJ1 resulted in an increased expression of DRAM1. Furthermore, silencing of DRAM1 substantially augmented the antitumor effect of FTSJ1 on NSCLC cells. Our findings suggested an important mechanism of tRNA modifications in NSCLC and demonstrated novel roles of FTSJ1 as both tRNA Am modifier and tumor suppressor in NSCLC.

tRNA modification and cancer: potential for therapeutic prevention and intervention

Transfer RNAs (tRNAs) undergo extensive chemical modification within cells through the activity of tRNA methyltransferase enzymes (TRMs). Although tRNA modifications are dynamic, how they impact cell behavior after stress and during tumorigenesis is not well understood. This review discusses how tRNA modifications influence the translation of codon-biased transcripts involved in responses to oxidative stress. We further discuss emerging mechanistic details about how aberrant TRM activity in cancer cells can direct programs of codon-biased translation that drive cancer cell phenotypes. The studies reviewed here predict future preventative therapies aimed at augmenting TRM activity in individuals at risk for cancer due to exposure. They further predict that attenuating TRM-dependent translation in cancer cells may limit disease progression while leaving noncancerous cells unharmed.

Quercetin inhibits human metastatic ovarian cancer cell growth and modulates components of the intrinsic apoptotic pathway in PA-1 cell line

Ovarian cancer is the leading cause of gynaecology related cancer death worldwide. It is often diagnosed with an advanced stage. Apoptosis is a process of programmed cell death controlled by cell cycle machinery and several signaling pathways. Plant-derived compounds have received an increased interest in the treatment of cancer. Quercetin is a flavonoid present in fruits and vegetables which possess anticancer properties. Several studies have been demonstrated that quercetin induces apoptosis in various cancers. However, the apoptotic role of quercetin in metastatic ovarian cancer has not been extensively studied. In the present study, we investigated the apoptotic effect of quercetin on human metastatic ovarian cancer PA-1 cell line. Quercetin treatment (0-200 μM) for 24h decreases PA-1 cells viability in a dose-dependent manner. The effective dose was identified as 50 and 75 μM based on MTT assay. Quercetin induces apoptosis in metastatic ovarian cancer cells which were confirmed by AO/EtBr dual staining, DAPI staining and DNA fragmentation assay. Molecules involved in the intrinsic apoptotic pathway were altered by quercetin. Interestingly, antiapoptotic molecules such as Bcl-2, Bcl-xL were decreased while proapoptotic molecules such as caspase-3, caspase-9, Bid, Bad, Bax and cytochrome c were increased in the quercetin-treated PA-1 cells. Our results indicate that quercetin induces mitochondrial-mediated apoptotic pathway and thus it inhibits the growth of metastatic ovarian cancer cells.

tRNA-Derived Small RNAs: Biogenesis, Modification, Function and Potential Impact on Human Disease Development

Transfer RNAs (tRNAs) are abundant small non-coding RNAs that are crucially important for decoding genetic information. Besides fulfilling canonical roles as adaptor molecules during protein synthesis, tRNAs are also the source of a heterogeneous class of small RNAs, tRNA-derived small RNAs (tsRNAs). Occurrence and the relatively high abundance of tsRNAs has been noted in many high-throughput sequencing data sets, leading to largely correlative assumptions about their potential as biologically active entities. tRNAs are also the most modified RNAs in any cell type. Mutations in tRNA biogenesis factors including tRNA modification enzymes correlate with a variety of human disease syndromes. However, whether it is the lack of tRNAs or the activity of functionally relevant tsRNAs that are causative for human disease development remains to be elucidated. Here, we review the current knowledge in regard to tsRNAs biogenesis, including the impact of RNA modifications on tRNA stability and discuss the existing experimental evidence in support for the seemingly large functional spectrum being proposed for tsRNAs. We also argue that improved methodology allowing exact quantification and specific manipulation of tsRNAs will be necessary before developing these small RNAs into diagnostic biomarkers and when aiming to harness them for therapeutic purposes.

Phosphorylation of human TRM9L integrates multiple stress-signaling pathways for tumor growth suppression

The human transfer RNA methyltransferase 9-like gene (TRM9L, also known as KIAA1456) encodes a negative regulator of tumor growth that is frequently silenced in many forms of cancer. While TRM9L can inhibit tumor cell growth in vivo, the molecular mechanisms underlying the tumor inhibition activity of TRM9L are unknown. We show that oxidative stress induces the rapid and dose-dependent phosphorylation of TRM9L within an intrinsically disordered domain that is necessary for tumor growth suppression. Multiple serine residues are hyperphosphorylated in response to oxidative stress. Using a chemical genetic approach, we identified a key serine residue in TRM9L that undergoes hyperphosphorylation downstream of the oxidative stress-activated MEK (mitogen-activated protein kinase kinase)-ERK (extracellular signal-regulated kinase)-RSK (ribosomal protein S6 kinase) signaling cascade. Moreover, we found that phosphorylated TRM9L interacts with the 14-3-3 family of proteins, providing a link between oxidative stress and downstream cellular events involved in cell cycle control and proliferation. Mutation of the serine residues required for TRM9L hyperphosphorylation and 14-3-3 binding abolished the tumor inhibition activity of TRM9L. Our results uncover TRM9L as a key downstream effector of the ERK signaling pathway and elucidate a phospho-signaling regulatory mechanism underlying the tumor inhibition activity of TRM9L.

Above the Epitranscriptome: RNA Modifications and Stem Cell Identity

Sequence databases and transcriptome-wide mapping have revealed different reversible and dynamic chemical modifications of the nitrogen bases of RNA molecules. Modifications occur in coding RNAs and noncoding-RNAs post-transcriptionally and they can influence the RNA structure, metabolism, and function. The result is the expansion of the variety of the transcriptome. In fact, depending on the type of modification, RNA molecules enter into a specific program exerting the role of the player or/and the target in biological and pathological processes. Many research groups are exploring the role of RNA modifications (alias epitranscriptome) in cell proliferation, survival, and in more specialized activities. More recently, the role of RNA modifications has been also explored in stem cell biology. Our understanding in this context is still in its infancy. Available evidence addresses the role of RNA modifications in self-renewal, commitment, and differentiation processes of stem cells. In this review, we will focus on five epitranscriptomic marks: N6-methyladenosine, N1-methyladenosine, 5-methylcytosine, Pseudouridine (Ψ) and Adenosine-to-Inosine editing. We will provide insights into the function and the distribution of these chemical modifications in coding RNAs and noncoding-RNAs. Mainly, we will emphasize the role of epitranscriptomic mechanisms in the biology of naïve, primed, embryonic, adult, and cancer stem cells.