Sensitive and Simultaneous Determination of Uridine Thiolation and Hydroxylation Modifications in Eukaryotic RNA by Derivatization Coupled with Mass Spectrometry Analysis.

The discovery of dynamic and reversible modifications in RNA expands their functional repertoires. Now, RNA modifications have been viewed as new regulators involved in a variety of biological processes. Among these modifications, thiolation is one kind of special modification in RNA. Several thiouridines have been identified to be present in RNA, and they are essential in the natural growth and metabolism of cells. However, detection of these thiouridines generally is challenging, and few studies could offer the quantitative levels of uridine modifications in RNA, which limits the in-depth elucidation of their functions. Herein, we developed a chemical derivatization in combination with mass spectrometry analysis for the sensitive and simultaneous determination of uridine thiolation and hydroxylation modifications in eukaryotic RNA. The chemical derivatization strategy enables the addition of easily ionizable groups to the uridine thiolation and hydroxylation modifications, leading up to a 339-fold increase in detection sensitivities of these modifications by mass spectrometry analysis. The limits of detection of these uridine modifications can be down to 17 amol. With the established method, we discovered and confirmed that a new modification of 5-hydroxyuridine (ho5U) was widely present in small RNAs of mammalian cells, expanding the diversity of RNA modifications. The developed method shows superior capability in determining low-abundance RNA modifications and may promote identifying new modifications in RNA, which should be valuable in uncovering the unknown functions of RNA modifications.

Methods for isolation of messenger RNA from biological samples.

RNA molecules contain many chemical modifications that can regulate a variety of biological processes. Messenger RNA (mRNA) molecules are critical components in the central dogma of molecular biology. The discovery of reversible chemical modifications in eukaryotic mRNA brings forward a new research field in RNA modification-mediated regulation of gene expression. The modifications in mRNA generally exist in low abundance. The use of highly pure mRNA is critical for the confident identification of new modifications as well as for the accurate quantification of existing modifications in mRNA. In addition, isolation of highly pure mRNA is the first step in many biological research studies. Therefore, the methods for isolating highly pure mRNA are important for mRNA-based downstream studies. A variety of methods for isolating mRNA have been developed in the past few decades and new methods continuously emerge. This review focuses on the methodologies and protocols for isolating mRNA populations. In addition, we discuss the advantages and limitations of these methods. We hope this paper will provide a general view of mRNA isolation strategies and facilitate studies that involve mRNA modifications and functions.

P2P lending platforms in Malaysia: What do we know?

Background - With the recent evolution of Financial Technology (FinTech), 11 peers to peer (P2P) lending platforms have been regulated by the Securities Commission in Malaysia since 2016. P2P lending platforms offer new investment opportunities to individual investors to earn higher rates on return than what traditional lenders usually provide. However, individual investors may face higher potential risks of default from their borrowers. Therefore, individual investors need to understand the potential exposure to such P2P lending platforms to make an effective investment decision. This study aims to explore the potential risk exposures that individual investors may experience at Malaysia's licensed P2P lending platforms.   Methods - Based on data collected manually from nine P2P lending platforms over five months, relationships between interest rates and various risk classifying factors such as credit rating, industry, business stage, loan purpose, and loan duration are examined.    Results- This study shows that loans with a similar credit rating and with or without similar loan purpose; and a business stage may offer investors significantly different interest rates. In addition, loans with shorter durations may provide investors with higher interest rates than those with longer durations. Finally, loans issued by companies from the same industry appeared to be charged with similar interest. These findings are valuable to investors to prepare themselves before making their investments at the P2P lending platforms.   Conclusion- With first hand-collected data, this study provides an original insight into Malaysia's current P2P lending platforms. Findings obtained for relationships between interest rates and risk classifying factors such as credit rating, industry, business stage, loan purpose and loan duration are valuable to investors of Malaysian P2P lending platforms.

Novel dual methylation of cytidines in the RNA of mammals.

RNA modifications play critical roles in regulating a variety of physiological processes. Methylation is the most prevalent modification occurring in RNA. Three isomeric cytidine methylation modifications have been reported in RNA, including 3-methylcytidine (m3C), N4-methylcytidine (m4C), and 5-methylcytidine (m5C), in mammals. Aside from the single methylation on the nucleobase of cytidines, dual methylation modifications occurring in both the 2' hydroxyl of ribose and the nucleobase of cytidines also have been reported, including N4,2'-O-dimethylcytidine (m4Cm) and 5,2'-O-dimethylcytidine (m5Cm). m4Cm has been found in the 16S rRNA of E. coli, while m5Cm has been found in the tRNA of terminal thermophilic archaea and mammals. However, unlike m4Cm and m5Cm, the presumed dual methylation of 3,2'-O-dimethylcytidine (m3Cm) has never been discovered in living organisms. Thus, the presence of m3Cm in RNA remains an open question. In the current study, we synthesized m3Cm and established a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method to determine the dimethylation of cytidines, m3Cm, m4Cm and m5Cm. Under optimized analytical conditions, m3Cm, m4Cm and m5Cm can be clearly distinguished. Using the method, we discovered the existence of m3Cm in the RNA of mammals. The identified m3Cm is a novel modification that hasn't been reported in the three-domain system, including archaea, bacteria, and eukaryotes. We confirmed that m3Cm mainly existed in the small RNA (<200 nt) of mammals. In addition, we identified, for the first time, the presence of m4Cm in the 18S rRNA of mammalian cells. The stable isotope tracing monitored by mass spectrometry demonstrated that S-adenosyl-l-methionine was a methyl donor for all three dimethylations of cytidines in RNA. The discovery of m3Cm broadens the diversity of RNA modifications in living organisms. In addition, the discovery of m3Cm and m4Cm in mammals opens new directions in understanding RNA modification-mediated RNA processing and gene expression regulation.