Biophysical Analyses for Schizosaccharomyces pombe AAA+ ATPase Abo1

Abstract

Chromatin dynamically alters according to cell cycles and DNA metabolic events. One key factor for the chromatin dynamics is histone chaperones that serve nucleosome assembly and disassembly and play important roles in regulating gene expression as well as for maintaining epigenetic information. It has been reported that nucleosome arrangements are modulated by bromodomain-containing AAA+ ATPases in a broad range of eukaryotes. Here we have studied a Schizosaccharomyces pombe AAA+ ATPase Abo1, a homologue of human ATAD2 that is involved in diverse types of cancers. Although the biological roles of ATAD2 have been unveiled, the biological activities and structure of Abo1 have not been characterized yet. In particular, nucleosome organization by Abo1 remains unclear and debatable. To address those questions, we firstly revealed the Abo1 structure using cryo-EM. Abo1 displays a closed hexameric ring structure and a spiral hexameric structure in the presence of ADP and ATP, respectively. We also observed the conformational change of Abo1 depending on ATP hydrolysis in real time using a high-speed AFM imaging and demonstrated that Abo1 stochastically hydrolyzes ATP. Furthermore, we manifested that Abo1 does not dislodge but assembles histones depending on ATP hydrolysis using a novel high-throughput single-molecule imaging technique, DNA curtain.