RESUMEN
N6-methyladenosine (m6A) is a crucial RNA modification that regulates diverse biological processes in human cells, but its co-transcriptional deposition and functions remain poorly understood. Here, we identified the RNA helicase DDX21 with a previously unrecognized role in directing m6A modification on nascent RNA for co-transcriptional regulation. DDX21 interacts with METTL3 for co-recruitment to chromatin through its recognition of R-loops, which can be formed co-transcriptionally as nascent transcripts hybridize onto the template DNA strand. Moreover, DDX21's helicase activity is needed for METTL3-mediated m6A deposition onto nascent RNA following recruitment. At transcription termination regions, this nexus of actions promotes XRN2-mediated termination of RNAPII transcription. Disruption of any of these steps, including the loss of DDX21, METTL3, or their enzymatic activities, leads to defective termination that can induce DNA damage. Therefore, we propose that the R-loop-DDX21-METTL3 nexus forges the missing link for co-transcriptional modification of m6A, coordinating transcription termination and genome stability.
Asunto(s)
Adenosina , Adenosina/análogos & derivados , ARN Helicasas DEAD-box , Exorribonucleasas , Inestabilidad Genómica , Metiltransferasas , Estructuras R-Loop , ARN Polimerasa II , Terminación de la Transcripción Genética , Humanos , ARN Helicasas DEAD-box/metabolismo , ARN Helicasas DEAD-box/genética , Metiltransferasas/metabolismo , Metiltransferasas/genética , Adenosina/metabolismo , Adenosina/genética , Exorribonucleasas/metabolismo , Exorribonucleasas/genética , ARN Polimerasa II/metabolismo , ARN Polimerasa II/genética , Células HEK293 , Cromatina/metabolismo , Cromatina/genética , Daño del ADN , Células HeLa , ARN/metabolismo , ARN/genética , Transcripción Genética , Metilación de ARNRESUMEN
OBJECTIVE: To investigate the effect of Lishi No.5 formula on the growth of human neuroblastoma cell line SY5Y and find out the most effective drug dose. METHOD: SY5Y cells were administrated by Lishi No.5 formula in different concentration. MTT metabolic rate was measured as the cell survival rate, then the dose-effect curve was made. LDH leakage rate, axonal length and area of cell body were used as the indicators. RESULT: In 0.125-0.75 g x L(-1) Lishi No. 5 formula could increase the cell survival rate and MTT metabolic rate, decreased LDH leakage rate, and enhance axonal length and area of cell body, compared with control group. CONCLUSION: Lishi No.5 formula has the neurotrophic effect and can induce the survival of neuron.