Structural insights into apoptotic DNA degradation by CED-3 protease suppressor-6 (CPS-6) from Caenorhabditis elegans

Jason L.J. Lin, Akihisa Nakagawa, Chia Liang Lin, Yu-Yuan Hsiao, Wei Zen Yang, Yi Ting Wang, Lyudmila G. Doudeva, Riley Robert Skeen-Gaar, Ding Xue, Hanna S. Yuan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Endonuclease G (EndoG) is a mitochondrial protein that traverses to the nucleus and participates in chromosomal DNA degradation during apoptosis in yeast, worms, flies, and mammals. However, it remains unclear how EndoG binds and digests DNA. Here we show that the Caenorhabditis elegans CPS-6, a homolog of EndoG, is a homodimeric Mg 2+ -dependent nuclease, binding preferentially to G-tractDNAin the optimum low salt buffer at pH 7. The crystal structure of CPS-6 was determined at 1.8 Å resolution, revealing a mixed αβ topology with the two ββα-metal finger nuclease motifs located distantly at the two sides of the dimeric enzyme. A structural model of the CPS-6-DNA complex suggested a positively charged DNA-binding groove near the Mg 2+ -bound active site. Mutations of four aromatic and basic residues: Phe 122 , Arg 146 , Arg 156 , and Phe 166 , in the protein-DNA interface significantly reduced the DNA binding and cleavage activity of CPS-6, confirming that these residues are critical for CPS-6-DNA interactions. In vivo transformation rescue experiments further showed that the reduced DNase activity of CPS-6 mutants was positively correlated with its diminished cell killing activity in C. elegans. Taken together, these biochemical, structural, mutagenesis, and in vivo data reveal a molecular basis of how CPS-6 binds and hydrolyzes DNA to promote cell death.

Original languageEnglish
Pages (from-to)7110-7120
Number of pages11
JournalJournal of Biological Chemistry
Volume287
Issue number10
DOIs
StatePublished - 2 Mar 2012

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