APOBEC3B

A research team has discovered the key role that the APOBEC3A and APOBEC3B enzymes play in driving cancer mutations by modifying the DNA in tumor genomes, offering potential new targets for intervention strategies. A research team led by the University of California, Irvine has discovered the key role that the APOBEC3A and APOBEC3B enzymes play in driving cancer mutations by modifying the DNA in tumor genomes, offering potential new targets for intervention strategies. The study, published today online in the journal Nature Communications, describes how the researchers identified the process by which APOBEC3A and APOBEC3B detect specific DNA structures, resulting in mutations at distinct positions within the tumor genome. "It's critical to understand how cancer cells accumulate mutations leading to hot spots that contribute to disease progression, drug resistance and metastasis," said corresponding author Rémi Buisson, UCI assistant professor of biological chemistry. "Both APOBEC3A and APOBEC3B were known to generate mutations in many kinds of tumors, but until now we did not know how to identify the specific type caused by each. This finding will allow us to develop novel therapies to suppress mutation formation by directly targeting each enzyme accordingly." In this study, graduate student Ambrocio Sanchez and postdoctoral fellow Pedro Ortega, both in Buisson's laboratory at the UCI School of Medicine, developed a new method to characterize the particular kind of DNA modified by APOBEC3A and APOBEC3B. It revealed that the two enzymes do not recognize the same DNA sequences and structures within the genomes of cancer cells. Based on this observation, an innovative approach utilizing these unique target preferences was employed to classify cancer patients who had accumulated mutations caused by each enzyme. "The next steps are to investigate whether mutations caused by these enzymes lead to various types of therapy resistance. It's also critical to identify molecules that inhibit APOBEC3A and APOBEC3B to prevent mutations from forming. Our findings could, in the future, help to assess patient risk before treatment and suppress tumor evolution using the appropriate drug therapy," Buisson said. Other team members included undergraduate and graduate students and postdoctoral fellows from UCI, Harvard Medical School, the University of Southern California, the University of Texas at San Antonio and the University of Minnesota. This work was supported by the National Institutes of Health's Research Supplements to Promote Diversity in Health-Related Research program under award R37-CA252081-S; California Institute for Regenerative Medicine stem cell biology training grant TG2-01152; European Molecular Biology Organization postdoctoral fellowship ALTF 213-2023; Cancer Prevention and Research Institute of Texas research training award RP 170345 and Recruitment of Established Investigators award CPRIT RR220053; the National Cancer Institute under awards R37-VA252081 and P01-CA234228; the National Institute of Allergy and Infectious Diseases under award R01 AI150524; and access to UCI's Genomics Research and Technology Hub, affiliated with the Chao Family Comprehensive Cancer Center, under grant P30-CA062203.

A new study uncovers how a protein, APOBEC3B, could protects cells against many different types of RNA viruses like respiratory syncytial virus (RSV), SARS-CoV2, influenza virus, poliovirus and measles, helping to prevent disease. A new University of California, Irvine-led study uncovers how a protein, APOBEC3B, could protects cells against many different types of RNA viruses like respiratory syncytial virus (RSV), SARS-CoV2, influenza virus, poliovirus and measles, helping to prevent disease. The study was published in Nature Communications. Titled, "APOBEC3B drives PKR-mediated translation shutdown and protects stress granules in response to viral infection," the study findings provide an understanding of how lung cells, in particular, protect themselves against RNA viral infection. This new discovery is essential to developing future therapies to limit viral infection and improve the health of patients with chronic lung disease. Respiratory syncytial virus (RSV), SARS-CoV2, influenza virus, poliovirus, and measles -- all single-stranded RNA viruses -- are some examples of highly contagious diseases transmitted by respiratory aerosols that commonly infect lung cells. "Patients with chronic lung diseases, such as asthma, cystic fibrosis, chronic obstructive pulmonary disease and interstitial lung diseases, are more susceptible to respiratory lung infections. These viral infections can further contribute to disease progression," said Remi Buisson, PhD, assistant professor in the UCI School of Medicine Department of Biological Chemistry. "An exciting part of our finding fills a critical knowledge gap by illuminating how APOBEC3B can promote innate immune responses in host cells without generating mutations in the virus genomes and promoting viral evolution." In this study, graduate students Lavanya Manjunath and Sunwoo Oh, both at UCI School of Medicine in the Buisson Laboratory, utilized different RNA virus models, including Sendai virus, poliovirus, and Sindbis virus as tools to determine how APOBEC3B regulates innate immune signaling in response to viral infection. Moreover, they found that APOBEC3B is recruited to stress granules through its interaction with PABPC1 to prevent stress granule destabilization and protect mRNAs associated with stress granules from an RNA endonuclease RNase L that cleave RNAs in host cells. "We propose that APOBEC3B, in addition to its canonical role to edit viral genomes, functions with PABPC1 as important innate immunity mediators, protecting cells at different steps of the innate immune response against viral infections," said Buisson. More research is needed to develop strategies to prevent RNA viral infection. "Our next steps are to determine the detailed mechanism of how APOBEC3B recognizes viral genome to promote an innate immune response and prevent viral replication," said Buisson. "The goal is to identify how RNA viruses developed resistance mechanisms to counteract APOBEC3B functions and escape host cell defense." The study was funded by support from the National Institutes of Health.