# Base preference for inosine 3′-riboendonuclease activity of human endonuclease V: implications for cleavage of poly-A tails containing inosine

## TL;DR

The study explores how human endonuclease V cleaves RNA containing inosine, revealing its role in maintaining RNA quality by targeting specific base preferences.

## Contribution

The study identifies the base preference of hEndoV for cleaving RNA with inosine, providing new insight into its in vivo function.

## Key findings

- hEndoV cleavage activity is highest with 2′-OH modification in ribose.
- hEndoV shows specificity for adenine at the 3′-end of hypoxanthine at the cleavage site.
- hEndoV recognizes and cleaves inosine on poly A tails to maintain RNA quality.

## Abstract

Deamination of bases is a form of DNA damage that occurs spontaneously via the hydrolysis and nitrosation of living cells, generating hypoxanthine from adenine. E. coli endonuclease V (eEndoV) cleaves hypoxanthine-containing double-stranded DNA, whereas human endonuclease V (hEndoV) cleaves hypoxanthine-containing RNA; however, hEndoV in vivo function remains unclear. To date, hEndoV has only been examined using hypoxanthine, because it binds closely to the base located at the cleavage site. Here, we examined whether hEndoV cleaves other lesions (e.g., AP site, 6-methyladenine, xanthine) to reveal its function and whether 2′-nucleoside modification affects its cleavage activity. We observed that hEndoV is hypoxanthine-specific; its activity was the highest with 2′-OH modification in ribose. The cleavage activity of hEndoV was compared based on its base sequence. We observed that it has specificity for adenine located on the 3′-end of hypoxanthine at the cleavage site, both before and after cleavage. These data suggest that hEndoV recognizes and cleaves the inosine generated on the poly A tail to maintain RNA quality. Our results provide mechanistic insight into the role of hEndoV in vivo.