Source: School of Pharmaceutical Sciences
Written by: School of Pharmaceutical Sciences
Edited by: Tan Rongyu, Wang Dongmei

The ATP and energy required for normal cell metabolism is mainly provided by oxidative phosphorylation of mitochondria, while tumor cells prefer glycolysis even if oxygen supply is sufficient. In recent years, the research on energy metabolism of tumor cells has been widely concerned, which will provide a new direction for tumor treatment. N6-methyladenine (m6A) mRNA modification has a variety of regulatory functions in cell biology including growth, proliferation and metastasis of tumor cells. However, whether m6A modification is involved in metabolic programming of tumor cells remained to be further studied.

Recently, Professor Hongsheng Wang's group at the School of Pharmaceutical Sciences of Sun Yat-sen University (SYSU) has made new progress in the research of m6A modification regulating metabolic programming of tumor cells. The study has been published in the journal of Nature Communications, entitled "N6-methyladenosine regulations glycolysis of cancer cells through PDK4".


In this study, the research group found that the m6A modification of RNA has a positive regulatory effect on the energy metabolism of tumor cells. It can participate in glycolysis and ATP production of tumor cells through pyruvate dehydrogenase kinase 4 (PDK4). Particularly, m6A modified 5’UTR of PKD4 positively regulates its translation elongation and mRNA stability via binding with YTHDF1/eEF-2 complex and IGF2BP3, respectively. Further, TATA-binding protein (TBP) can transcriptionally increase the expression of Mettl3 in cervical cancer cells via binding to its promoter. In vivo and clinical data confirm the positive roles of m6A/PDK4 in tumor growth and progression of cervical and liver cancer. This study reveals that m6A regulates glycolysis of cancer cells through PDK4.

On the other hand, the group published another research paper entitled "Targeted mRNA demethylation using an engineered dCas13b-ALKBH5 fusion protein" in the journal of Nucleic Acids Research, and successfully constructed a fusion protein system dm6ACRISPR based on dCas13b-ALKBH5 to achieve demethylation of targeted mRNA in living cells. At the same time, dm6ACRISPR targeting EGFR and MYC in tumor cells can significantly reduce their expression and inhibit the growth of tumor cells.

m6A is the most common post transcriptional modification in higher biological mRNA, which is controlled by "writer", "eraser" and "reader". Among them, FTO and ALKBH5 are demethylases that can "erase" the m6A modification on mRNA. However, the specific role of m6A modification in target mRNA has not been demonstrated in living cells. In recent years, gene editing technology based on CRISPR/Cas system has developed rapidly. Among them, the fusion protein system constructed by enzyme inactivated DNA binding enzyme dCas9 combined with functional protein can modify the epigenetic modification of DNA in living cells. Similar to Cas9, Cas13b can bind and cleave RNA, while enzyme inactivated Cas13b (dCaS13b) combined with gRNA can only bind to target mRNA without cleaving, which makes it possible for epigenetic modification and editing of mRNA in living cells.


In this study, dm6ACRISPR, which targets mRNA in living cells, was constructed by using dCas13b-ALKBH5 fusion and gRNA. The dm6ACRISPR system has the characteristics of high specificity, high demethylation efficiency and low miss rate. Results showed that dm6ACRISPR could demethylate the single site of CYB5A mRNA and multiple sites of CTNNB1 mRNA, and increases the stability of target mRNA. At the same time, dm6ACRISPR is high mismatch intolerance, and the rate of off-target is only 0.03%. In addition, targeting EGFR and MYC in tumor cells with dm6ACRISPR system can significantly reduce the expression level of EGFR and MYC, and significantly inhibit the growth of tumor cells, indicating that dm6ACRISPR has potential value in disease prevention and treatment.

The above research work was supported by the National Natural Science Foundation of China. It was supported by Professor Shuibin Lin at the First Affiliated Hospital of Sun Yat-sen University, and Professor Cheng-Ming Chiang at University of Texas Southwestern Medical Center.

Link to the paper: https://www.nature.com/articles/s41467-020-16306-5

     https://academic.oup.com/nar/article-lookup/doi/10.1093/nar/gkaa269