m(6)Am methyltransferase PCIF1 is essential for aggressiveness of gastric cancer cells by inhibiting TM9SF1 mRNA translation.

PCIF1 (phosphorylated CTD interacting factor 1) is the first reported RNA N6,2'-O-dimethyladenosine (m6Am) methyltransferase. However, the pathological significance of PCIF1 and m6Am modification remains unknown. Here we find that both PCIF1 expression and m6Am modification are significantly elevated in gastric cancer tissues. Increased PCIF1 is associated with gastric cancer progression, and predicts poor prognosis. Silence of PCIF1 inhibits the proliferation and invasion of gastric cancer cells, and suppresses tumor growth and metastasis in mouse model. m6Am-seq analysis reveals TM9SF1 (transmembrane 9 superfamily member 1) as a target of PCIF1. PCIF1 modifies TM9SF1 mRNA with m6Am leading to decreased TM9SF1 translation. TM9SF1 reverses the effects of PCIF1 on gastric cancer cell aggressiveness. Collectively, our work uncovers an oncogenic function of PCIF1, providing insights into the critical role of m6Am modification in cancer progression.

Zhuo W ，Sun M ，Wang K ，Zhang L ，Li K ，Yi D ，Li M ，Sun Q ，Ma X ，Liu W ，Teng L ，Yi C ，Zhou T ... -  《Cell Discovery》

HIV reprograms host m(6)Am RNA methylome by viral Vpr protein-mediated degradation of PCIF1.

N6,2'-O-dimethyladenosine (m6Am) is an abundant RNA modification located adjacent to the 5'-end of the mRNA 7-methylguanosine (m7G) cap structure. m6A methylation on 2'-O-methylated A at the 5'-ends of mRNAs is catalyzed by the methyltransferase Phosphorylated CTD Interacting Factor 1 (PCIF1). The role of m6Am and the function of PCIF1 in regulating host-pathogens interactions are unknown. Here, we investigate the dynamics and reprogramming of the host m6Am RNA methylome during HIV infection. We show that HIV infection induces a dramatic decrease in m6Am of cellular mRNAs. By using PCIF1 depleted T cells, we identify 2237 m6Am genes and 854 are affected by HIV infection. Strikingly, we find that PCIF1 methyltransferase function restricts HIV replication. Further mechanism studies show that HIV viral protein R (Vpr) interacts with PCIF1 and induces PCIF1 ubiquitination and degradation. Among the m6Am genes, we find that PCIF1 inhibits HIV infection by enhancing a transcription factor ETS1 (ETS Proto-Oncogene 1, transcription factor) stability that binds HIV promoter to regulate viral transcription. Altogether, our study discovers the role of PCIF1 in HIV-host interactions, identifies m6Am modified genes in T cells which are affected by viral infection, and reveals how HIV regulates host RNA epitranscriptomics through PCIF1 degradation.

Zhang Q ，Kang Y ，Wang S ，Gonzalez GM ，Li W ，Hui H ，Wang Y ，Rana TM ... -  《Nature Communications》

m(6)Am Methyltransferase PCIF1 Regulates Periodontal Inflammation.

Song W ，Liu L ，Liang H ，Cheng H ，He W ，Yin Q ，Zhang Z ，Lin W ，Li H ，Li Q ，Liu W ，Zhang D ，Chen D ，Yuan Q ... -  《-》

Enzymatic characterization of mRNA cap adenosine-N6 methyltransferase PCIF1 activity on uncapped RNAs.

The phosphorylated RNA polymerase II CTD interacting factor 1 (PCIF1) is a methyltransferase that adds a methyl group to the N6-position of 2'O-methyladenosine (Am), generating N6, 2'O-dimethyladenosine (m6Am) when Am is the cap-proximal nucleotide. In addition, PCIF1 has ancillary methylation activities on internal adenosines (both A and Am), although with much lower catalytic efficiency relative to that of its preferred cap substrate. The PCIF1 preference for 2'O-methylated Am over unmodified A nucleosides is due mainly to increased binding affinity for Am. Importantly, it was recently reported that PCIF1 can methylate viral RNA. Although some viral RNA can be translated in the absence of a cap, it is unclear what roles PCIF1 modifications may play in the functionality of viral RNAs. Here we show, using in vitro assays of binding and methyltransfer, that PCIF1 binds an uncapped 5'-Am oligonucleotide with approximately the same affinity as that of a cap analog (KM = 0.4 versus 0.3 μM). In addition, PCIF1 methylates the uncapped 5'-Am with activity decreased by only fivefold to sixfold compared with its preferred capped substrate. We finally discuss the relationship between PCIF1-catalyzed RNA methylation, shown here to have broader substrate specificity than previously appreciated, and that of the RNA demethylase fat mass and obesity-associated protein (FTO), which demonstrates PCIF1-opposing activities on capped RNAs.

Yu D ，Dai N ，Wolf EJ ，Corrêa IR Jr ，Zhou J ，Wu T ，Blumenthal RM ，Zhang X ，Cheng X ... -  《-》

PCIF1, the only methyltransferase of N6,2-O-dimethyladenosine.

Wu Y ，Pu X ，Wu S ，Zhang Y ，Fu S ，Tang H ，Wang X ，Xu M ... -  《Cancer Cell International》