A dual role of human tRNA methyltransferase hTrmt13 in regulating translation and transcription

Decoding the role of tRNA modifications in cancer progression

Epitranscriptomic modification of tRNA has recently gained traction in the field of cancer biology. The presence of such modifications on tRNA appears to allow for translational control of processes central to progression and malignant transformation. Methyltransferase Like 1 protein (METTL1), along with other epitranscriptomic writers (e.g. NSUN3, NAT10, ELP3, etc.), has recently been investigated in multiple cancer types. Here, we review the impact of such tRNA modifications in tumorigenesis and the progression of cancer toward drug resistance and metastasis. Regulation of central cellular processes relied upon by malignant cancer cells through modulation of the tRNA epitranscriptome represents an area with great potential to bring novel first-in-class therapies to the clinic.

Non‐m6A RNA modifications in haematological malignancies

Dysregulated RNA modifications, stemming from the aberrant expression and/or malfunction of RNA modification regulators operating through various pathways, play pivotal roles in driving the progression of haematological malignancies. Among RNA modifications, N6-methyladenosine (m6A) RNA modification, the most abundant internal mRNA modification, stands out as the most extensively studied modification. This prominence underscores the crucial role of the layer of epitranscriptomic regulation in controlling haematopoietic cell fate and therefore the development of haematological malignancies. Additionally, other RNA modifications (non-m6A RNA modifications) have gained increasing attention for their essential roles in haematological malignancies. Although the roles of the m6A modification machinery in haematopoietic malignancies have been well reviewed thus far, such reviews are lacking for non-m6A RNA modifications. In this review, we mainly focus on the roles and implications of non-m6A RNA modifications, including N4-acetylcytidine, pseudouridylation, 5-methylcytosine, adenosine to inosine editing, 2'-O-methylation, N1-methyladenosine and N7-methylguanosine in haematopoietic malignancies. We summarise the regulatory enzymes and cellular functions of non-m6A RNA modifications, followed by the discussions of the recent studies on the biological roles and underlying mechanisms of non-m6A RNA modifications in haematological malignancies. We also highlight the potential of therapeutically targeting dysregulated non-m6A modifiers in blood cancer.

Roles and regulation of tRNA-derived small RNAs in animals

A growing class of small RNAs, known as tRNA-derived RNAs (tdRs), tRNA-derived small RNAs or tRNA-derived fragments, have long been considered mere intermediates of tRNA degradation. These small RNAs have recently been implicated in an evolutionarily conserved repertoire of biological processes. In this Review, we discuss the biogenesis and molecular functions of tdRs in mammals, including tdR-mediated gene regulation in cell metabolism, immune responses, transgenerational inheritance, development and cancer. We also discuss the accumulation of tRNA-derived stress-induced RNAs as a distinct adaptive cellular response to pathophysiological conditions. Furthermore, we highlight new conceptual advances linking RNA modifications with tdR activities and discuss challenges in studying tdR biology in health and disease.

TRMT13 inhibits the growth of papillary thyroid cancer by targeting ANAPC4

The recently discovered gene TRMT13 encodes a type of RNA methylase and is a member of the CCDC family (also called CCDC76). Here, we delineate its role in papillary thyroid cancer (PTC). Bioinformatics analysis shows significant TRMT13 and ANAPC4 downregulation in PTC and reveals that the expression levels of both genes are linearly correlated. Subsequent analyses confirm that both TRMT13 and ANAPC4 expressions are downregulated in PTC tissues and that this change in expression has a significant impact on cancer diagnosis. We conduct assays on PTC cells subjected to TRMT13 and ANAPC4 silencing or overexpression to assess the biological effects of these genes. We also perform rescue experiments to validate the regulatory effects of TRMT13 on ANAPC4. A nude mouse tumor model is used to evaluate the effects of TRMT13 and ANAPC4 on PTC tumorigenesis. TRMT13 expression is decreased in PTC tissues and cell lines and is positively correlated with that of ANAPC4. Cell assays reveal that TRMT13/ANAPC4 attenuates the malignancy of PTC cells by restraining cell proliferation, migration and invasion, while rescue experiments corroborate that ANAPC4 is a downstream target of TRMT13. In the nude mouse xenograft model, both TRMT13 and ANAPC4 inhibit tumor growth, and TRMT13 and ANAPC4 expression levels are significantly associated with survival. Taken together, these findings lead to the conclusion that TRMT13 inhibits PTC growth via ANAPC4, indicating a new role of TRMT13 and providing insights into the tRNA methyltransferase and coiled-coil domain-containing protein families.

The FERONIA-YUELAO module participates in translational control by modulating the abundance of tRNA fragments in Arabidopsis

tRNA fragments (tRFs) are a recently identified class of small noncoding RNAs. To date, the regulation of tRF abundance and its functional mechanisms have been largely unclear in plants. We investigated how the Arabidopsis thaliana receptor kinase FERONIA (FER) regulates the abundance of tRFs to inhibit global mRNA translation. We demonstrate that FER regulates tRF abundance by directly phosphorylating the tRNA-binding protein YUELAO (YL) to modulate its function. Downregulation of FER and YL prevented the modification of tRNA via cytosine-5-methylation and 2'-O-methylation, thereby increasing tRF abundance. Furthermore, we show that YL acts as an important genetic downstream target of FER signaling, and knockdown of a specific tRF partially rescues the root hair growth defects of fer and yl mutants. Our findings shed light on the abundance and regulatory mechanisms of tRF and their role in inhibiting translation in plants.

RNA modifications in cancer

Currently, more than 170 modifications have been identified on RNA. Among these RNA modifications, various methylations account for two-thirds of total cases and exist on almost all RNAs. Roles of RNA modifications in cancer are garnering increasing interest. The research on m6A RNA methylation in cancer is in full swing at present. However, there are still many other popular RNA modifications involved in the regulation of gene expression post-transcriptionally besides m6A RNA methylation. In this review, we focus on several important RNA modifications including m1A, m5C, m7G, 2'-O-Me, Ψ and A-to-I editing in cancer, which will provide a new perspective on tumourigenesis by peeking into the complex regulatory network of epigenetic RNA modifications, transcript processing, and protein translation.

A comprehensive comparative study on LSD1 in different cancers and tumor specific LSD1 inhibitors

LSD1 was significantly over-expressed in several cancer types, and its aberrant overexpression was revealed to play a crucial role in the initiation and progression of cancer. Several LSD1 inhibitors that were discovered and developed so far were found to be effective in attenuating tumor growth in both in vivo and in vitro studies. However, the major challenge associated with the development of cancer therapies is personalized treatment. Therefore, it is essential to look in detail at how LSD1 plays its part in carcinogenesis and whether there are any different expression levels of LSD1 in different tumors. Here in this review, fresh insight into a list of function correlated LSD1 binding proteins are provided, and we tried to figure out the role of LSD1 in different cancer types, including hematological malignancies and solid tumors. A critical description of mutation preference for LSD1 in different tumors was also discussed. Recent research findings clearly showed that the abrogation of LSD1 demethylase activity via LSD1 inhibitors markedly reduced the growth of cancer cells. But there are still many ambiguities regarding the role of LSD1 in different cancers. Therefore, targeting LSD1 for treating different cancers is still reductionist, and many challenges need to be met to improve the therapeutic outcomes of LSD1 inhibitors.