Nuclear m(6)A Reader YTHDC1 Regulates mRNA Splicing.

The regulatory role of N(6)-methyladenosine (m(6)A) and its nuclear binding protein YTHDC1 in pre-mRNA splicing remains an enigma. Here we show that YTHDC1 promotes exon inclusion in targeted mRNAs through recruiting pre-mRNA splicing factor SRSF3 (SRp20) while blocking SRSF10 (SRp38) mRNA binding. Transcriptome assay with PAR-CLIP-seq analysis revealed that YTHDC1-regulated exon-inclusion patterns were similar to those of SRSF3 but opposite of SRSF10. In vitro pull-down assay illustrated a competitive binding of SRSF3 and SRSF10 to YTHDC1. Moreover, YTHDC1 facilitates SRSF3 but represses SRSF10 in their nuclear speckle localization, RNA-binding affinity, and associated splicing events, dysregulation of which, as the result of YTHDC1 depletion, can be restored by reconstitution with wild-type, but not m(6)A-binding-defective, YTHDC1. Our findings provide the direct evidence that m(6)A reader YTHDC1 regulates mRNA splicing through recruiting and modulating pre-mRNA splicing factors for their access to the binding regions of targeted mRNAs.

The multifaceted genus Acinetobacter: from infection to bioremediation.

Acinetobacter is a vast bacterial genus comprising of numerous species with variable characteristics. The enigma associated with clinical strains that have been implicated in many nosocomial outbreaks has prompted the need for continuous research on pathogens like Acinetobacter baumannii and members of the ACB complex. However, numerous species of Acinetobacter genus possess diverse metabolic capabilities and have the potential for a plethora of industrial and environment-based applications. Therefore, a comprehensive review on the entire genus, including many under-represented topics, would contribute extensive information to the scientific community indulged in Acinetobacter research. The current review is a unique compilation that attempts to provide the latest update on the genus covering its clinical as well as ecological aspects. Moreover, it is the first study of its kind that focuses on the entire genus and elaborates on the phylogenetic relationships, pathogenesis, and virulence mechanisms, followed by emerging biotechnological applications with future directions.

RNA m6A methyltransferase METTL3 regulates invasiveness of melanoma cells by matrix metallopeptidase 2.

The development of immunotherapy has improved the treatment of melanoma; however, resistance and frequent recurrence persist and remain a major problem. N-methyladenosine (mA) is the most abundant epitranscriptomic mark on mRNA and is essential for various physiological processes; however, its role in melanoma is unknown. Utilizing human normal melanocyte and melanoma cell lines, we analyzed the expression of METTL3 by quantitative RT-PCR. We inhibited the METTL3 expression by shRNA and analyzed the effects on melanoma cell proliferation, colony formation ability, and invasion. Finally, we assessed the role of METTL3 by using wild-type and mA catalytic site mutant METTL3. Melanoma cell lines express higher levels of METTL3, as compared with normal melanocytes. Interestingly, silencing of METTL3 gene expression in melanoma cells resulted in decreased mA activity, colony formation and invasiveness, while its overexpression led to increased mA activity, colony formation and invasion. METTL3 overexpression promotes accumulation of MMP2 and N-cadherin in melanoma cells. Strikingly, the overexpression of mA catalytic site mutant METTL3 was unable to produce a similar increase in MMP2 expression, suggesting that mA activity of METTL3 is important for melanoma cell invasiveness. Our results for the first time uncover the role of mA modification in melanoma cell biology. We show that METTL3 is upregulated in human melanoma and plays a role in invasion/migration through MMP2. These findings provide the framework for the development and use of METTL3 inhibitors in melanoma treatment.

Mammalian WTAP is a regulatory subunit of the RNA N6-methyladenosine methyltransferase.

The methyltransferase like 3 (METTL3)-containing methyltransferase complex catalyzes the N6-methyladenosine (m6A) formation, a novel epitranscriptomic marker; however, the nature of this complex remains largely unknown. Here we report two new components of the human m6A methyltransferase complex, Wilms' tumor 1-associating protein (WTAP) and methyltransferase like 14 (METTL14). WTAP interacts with METTL3 and METTL14, and is required for their localization into nuclear speckles enriched with pre-mRNA processing factors and for catalytic activity of the m6A methyltransferase in vivo. The majority of RNAs bound by WTAP and METTL3 in vivo represent mRNAs containing the consensus m6A motif. In the absence of WTAP, the RNA-binding capability of METTL3 is strongly reduced, suggesting that WTAP may function to regulate recruitment of the m6A methyltransferase complex to mRNA targets. Furthermore, transcriptomic analyses in combination with photoactivatable-ribonucleoside-enhanced crosslinking and immunoprecipitation (PAR-CLIP) illustrate that WTAP and METTL3 regulate expression and alternative splicing of genes involved in transcription and RNA processing. Morpholino-mediated knockdown targeting WTAP and/or METTL3 in zebrafish embryos caused tissue differentiation defects and increased apoptosis. These findings provide strong evidence that WTAP may function as a regulatory subunit in the m6A methyltransferase complex and play a critical role in epitranscriptomic regulation of RNA metabolism.