Molecular mechanism of DNA deadenylation by the neurological disease protein aprataxin.
The human neurological disease known as ataxia with oculomotor apraxia 1 is caused by mutations in the APTX gene that encodes Aprataxin (APTX) protein. APTX is a member of the histidine triad superfamily of nucleotide hydrolases and transferases but is distinct from other family members in that it acts upon DNA. The target of APTX is 5'-adenylates at DNA nicks or breaks that result from abortive DNA ligation reactions. In this work, we show that APTX acts as a nick sensor, which provides a mechanism to assess the adenylation status of unsealed nicks. When an adenylated nick is encountered by APTX, base pairing at the 5' terminus of the nick is disrupted as the adenylate is accepted into the active site of the enzyme. Adenylate removal occurs by a two-step process that proceeds through a transient AMP-APTX covalent intermediate. These results pinpoint APTX as the first protein to adopt canonical histidine triad-type reaction chemistry for the repair of DNA.
Rass
Ulrich
U
London Research Institute, Clare Hall Laboratories, Cancer Research UK, South Mimms, Herts EN6 3LD, United Kingdom.
Ahel
Ivan
I
West
Stephen C
SC
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002645:Chickens; D004247:DNA / Q000737:chemistry*; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000502:physiology*; D003850:Deoxyribonuclease I / Q000737:chemistry; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009422:Nervous System Diseases / Q000378:metabolism*; D009687:Nuclear Proteins / Q000737:chemistry* / Q000502:physiology*; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D017434:Protein Structure, Tertiary
C438188:APTX protein, human; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D004247:DNA; D003850:Deoxyribonuclease I