Recombinant BjADAT2 and BjADAT3 were individually expressed in E. coli and purified, and their enzyme activities were tested by in vitro tRNA deamination assay (Supplementary Fig. 4). Neither BjADAT2 nor BjADAT3 showed any A-to-I editing activity, but BjADAT2, in complex with BjADAT3, could perform A-to-I editing of amphioxus tRNA^Val_(AAC), and the apparent first-order deamination rate constant (k_app) of tRNA deamination was 0.0287 ± 0.00219 min⁻¹. Because the optimal RNA substrate for ADAT2 was the adenosines on the anticodon loop structure of tRNA, we wondered if BjADAT2 could mediate DNA deamination in a structure-specific fashion. Thus, we compared the deamination efficiency of BjADAT2 on DNA hairpin structure substrates (i.e., hpDNA-A and hpDNA-C, containing a single adenosine or cytidine in the loop region, respectively) and single-stranded linear structure substrates (i.e., ssDNA-A and ssDNA-C, containing a single adenosine or cytidine in the substrates, respectively). As shown in Fig. 3, both adenosine deamination of hpDNA-A and cytidine deamination of hpDNA-C were clearly observed under BjADAT2 treatment, and the change of the hairpin substrates to linear substrates resulted in about a threefold decrease in adenosine-and cytidine-deamination ratios. By contrast, no product band was seen in the lane of hpDNA-G or hpDNA-T treated with BjADAT2. Moreover, the BjADAT2-E58A protein purified in the same way as BjADAT2 showed no deamination activity (Supplementary Fig. 5f, g), ruling out the possibility that the observed deamination activity of BjADAT2 arose from a contaminant in the recombinant protein samples. In addition, BjADAT2-mediated adenosine-and cytidine deamination was inhibited by deoxycoformycin (DCF), an adenosine deaminase specific inhibitor, or tetrahydrouridine (THU), a cytidine deaminase specific inhibitor, or 1,10-o-phenanthroline, a zinc chelator. These indicated that BjADAT2 deaminated adenosine and cytidine in a zinc-dependent manner.

The k_app of BjADAT2-induced hpDNA-A deamination (0.00206 ± 0.00019 min⁻¹) was comparable with that of ABE7.10-induced DNA adenosine deamination (0.0010 ± 0.00030 min⁻¹)²². We compared the kinetics of BjADAT2-induced DNA deamination of the hairpin substrates and the linear substrates. The k_app was sixfold higher for the hpDNA-A substrate than for the ssDNA-A substrate (0.00032 ± 0.00004 min⁻¹). Similarly, the k_app was 24-fold higher for hpDNA-C (0.00801 ± 0.00037 min⁻¹) than for ssDNA-C (0.00033 ± 0.000026 min⁻¹) (Fig. 3e). These data together indicated that BjADAT2 preferentially deaminates adenosines and cytidines in the hairpin loop of substrates.

It was known that ADAT3, as a non-catalytic subunit, served a structural role in the adenosine deamination of tRNA^10,23. To date, only trypanosome ADAT2 was shown to be able to deaminate cytosines of DNA in the presence of ADAT3 in vitro⁶, but the specific role of the ADAT3 subunit in this DNA editing reaction was unclear. We demonstrated here that BjADAT3, though lacking catalytic function, could enhance the deamination activity of BjADAT2 toward hairpin structure substrates, including hpDNA-A and hpDNA-C (Fig. 3a, b). This was also supported by the results of kinetic analysis (Fig. 3e), which showed that the k_app of hpDNA-A deamination of BjADAT2/BjADAT3 complex (0.01092 ± 0.00062 min⁻¹) was 5.3-fold higher than that of BjADAT2 alone, and the k_app of hpDNA-C deamination by the complex (0.01066 ± 0.00083 min⁻¹) 1.3-fold higher than that of BjADAT2 alone. On the contrary, the k_app of ssDNA-A deamination of BjADAT2/BjADAT3 complex (0.00016 ± 0.

T cells are immune cells that fight off disease. The most common type of T cell, known as conventional T cells, maintains different functions, including activation of other T cells and killing pathogens. However, there is a less common type of T cell known as unconventional T cells. These cells regulate conventional T cells and often suppress conventional T cell function. How these cells develop and protect the body from infection and disease is unclear. Dr. Dan Pellicci and colleagues from Murdoch Children’s Research Institute and Federation University Australia reported on unconventional T cell development and their role in the immune system in a recent Science Immunology paper.

The researchers found that these unconventional T cells elicit an immune response. The discovery of an anti-pathogen role in these T cells has been unknown previously. Scientists can target these cells to prevent cancer and highly infectious diseases by understanding their role in immunity.

Dr. Pellicci and colleagues gathered samples from the Melbourne Children’s Heart Tissue Bank, where samples from children sixteen years old or younger who had heart surgery were kept. The researchers looked at the T cells from the thymus, a gland that further develops or matures T cells. After the T cells exit the thymus, they are ready to activate and target or kill infecting pathogens. Through T cell isolation, Dr. Pellicci and colleagues were able to determine the role of Unconventional T cells.

Ovarian cancer is the fourth-leading cause of cancer mortality among women and is characterized by late detection, extensive metastasis and poor prognosis.

One reason that treating this disease has been so challenging is that tumors often become resistant to chemotherapies, and generally respond poorly to immunotherapies.

While much of the research on overcoming resistance and efforts to develop new therapies have focused on the cancer cells, it has often ignored the many other cell types within the tumor. Indeed, cancer cells have the ability to reprogram the cells around them to nurture the tumor and help evade the patient’s immune system.