Nucleic Acids Research: TATDN2 resolution of R-loops is required for survival of BRCA1-mutant cancer cells (Sung, Gupta, Pertsemlidis, Bishop, et al)

Aruna S Jaiswal, Arijit Dutta, Gayathri Srinivasan, Yaxia Yuan, Daohong Zhou, Montaser Shaheen, Doraid T Sadideen, Austin Kirby, Elizabeth A Williamson, Yogesh K Gupta, Shaun K Olsen, Mingjiang Xu, Eva Loranc, Pramiti Mukhopadhyay, Alexander Pertsemlidis, Alexander J R Bishop, Patrick Sung, Jac A Nickoloff, Robert Hromas

BRCA1-deficient cells have increased IRE1 RNase, which degrades multiple microRNAs. Reconstituting expression of one of these, miR-4638–5p, resulted in synthetic lethality in BRCA1-deficient cancer cells. We found that miR-4638-5p represses expression of TATDN2, a poorly characterized member of the TATD nuclease family. We discovered that human TATDN2 has RNA 3′ exonuclease and endonuclease activity on double-stranded hairpin RNA structures. Given the cleavage of hairpin RNA by TATDN2 and the fact that BRCA1-deficient cells have difficulty resolving R-loops, we tested whether TATDN2 could resolve R-loops. Using in vitro biochemical reconstitution assays, we found TATDN2 bound to R-loops and degraded the RNA strand but not the DNA of multiple forms of R-loops in vitro in an Mg2+-dependent manner. Mutations in amino acids E593 and E705 predicted by Alphafold-2 to chelate an essential Mg2+ cation completely abrogated this R-loop resolution activity. Depleting TATDN2 increased cellular R-loops, DNA damage, and chromosomal instability. Loss of TATDN2 resulted in poor replication fork progression in the presence of increased R-loops. Significantly, we found that TATDN2 is essential for the survival of BRCA1-deficient cancer cells but much less so for cognate BRCA1-repleted cancer cells. Thus, we propose that TATDN2 is a novel target for therapy of BRCA1-deficient cancers.

Read Full Text

_________________________________________________________

Since 2004, UT Health San Antonio, Greehey Children’s Cancer Research Institute’s (Greehey CCRI) mission has been to advance scientific knowledge relevant to childhood cancer, contribute to understanding its causes, and accelerate the translation of knowledge into novel therapies. Greehey CCRI strives to have a national and global impact on childhood cancer by discovering, developing, and disseminating new scientific knowledge. Our mission consists of three key areas — research, clinical, and education.

Stay connected with the Greehey CCRI on Facebook, Twitter, LinkedIn, and Instagram.