NSun2 Promotes Cell Growth via Elevating Cyclin-Dependent Kinase 1 Translation

Abstract

cThe tRNA methytransferase NSun2 promotes cell proliferation, but the molecular mechanism has not been elucidated. Here, we report that NSun2 regulates cyclin-dependent kinase 1 (CDK1) expression in a cell cycle-dependent manner. Knockdown of NSun2 decreased the CDK1 protein level, while overexpression of NSun2 elevated it without altering CDK1 mRNA levels. Further studies revealed that NSun2 methylated CDK1 mRNA in vitro and in cells and that methylation by NSun2 enhanced CDK1 translation. Importantly, NSun2-mediated regulation of CDK1 expression had an impact on the cell division cycle. These results provide new insight into the regulation of CDK1 during the cell division cycle.

NSun2 delays replicative senescence by repressing p27 (KIP1) translation and elevating CDK1 translation

“…In agreement with the findings in Fig. 1B and in previous studies [28], neither overexpression of NSun2 nor knockdown of NSun2 altered the levels of p27 and CDK1 mRNAs in a measurable manner (Fig. 5B).…”

“…These results suggested that the regulation of p27 by NSun2 may not involve altered p27 mRNA transcription or turnover. Because NSun2 had been shown to regulate the expression of p53, p16, E2F3, Bak1, ErbB2, and CDK1 by methylating the mRNAs encoding these proteins [26–28], we tested if NSun2 was capable of methylating p27 mRNA. To this end, the p27 mRNA fragments described in Fig.…”

“…Apart from p27, NSun2 was also found to regulate the expression of senescence-associated proteins p53, p16, CDK1, and CDC25C [26–28]. To further investigate whether NSun2 regulated the process of replicative senescence, we assessed the levels of proteins NSun2, p53, p16, CDK1, p27, CDC25C, and GAPDH in early-passage [proliferating, ‘Young’ (Y), ~PDL 28], middle-passage [middle (M), ~PDL 40], and late-passage [senescent (S), ~PDL 55] human diploid fibroblasts (2BS) by Western blot analysis.…”

“…Our previous studies revealed that NSun2 methylates the 3′UTRs of mRNAs encoding p16, p53, E2F3, and ErbB2, thereby enhancing the expression of these proteins in cells exposed to oxidative stress [26–27]. NSun2-mediated mRNA methylation could also promote cell proliferation by elevating the translation of CDK1 [28]. However, the role of NSun2 in replicative senescence and the mechanisms underlying this process have not been studied.…”

RNA modifications and structures cooperate to guide RNA–protein interactions

“…Expression of the m 5 C writer NOP2/Sun RNA methyltransferase family member 2 (NSUN2) is tightly regulated during the cell cycle and its overexpression delays replicative senescence through methylation of Cyclin-dependent kinase 1 (CDK1) and the CDK inhibitor 1B (p27 KIP1 ) transcripts. Deposition of m 5 C in the CDK1 3′UTR enhances its translation, while m 5 C in the 5′UTR of p27 KIP1 represses its translation, resulting in increased cellular proliferation 56, 57 . Deposition of hm 5 C by methylcytosine dioxygenases 58 in mRNA correlates with higher association with polyribosomes in Drosophila melanogaster 59 .…”