Biochemical and Developmental Characterization of a SNF2-like ATPase Amplified in Liver Cancer 1 (ALC1)

Abstract

Post-translational modifications play a key role in recruiting chromatin remodeling and modifying enzymes to specific regions of chromosomes to modulate chromatin structure. Alc1 (Amplified in Liver Cancer 1), a member of the SNF2 ATPase superfamily with a carboxy-terminal macrodomain, is encoded by an oncogene implicated in the pathogenesis of hepatocellular carcinoma. Using a variety of biochemical techniques we show that Alc1 interacts transiently with chromatin associated proteins, including histones and the poly-(ADP-ribose) polymerase Parp1. Alc1 ATPase and chromatin remodeling activities are strongly activated by Parp1 and its substrate NAD and require an intact macrodomain capable of binding poly-(ADP-ribose). Alc1 is rapidly recruited to nucleosomes in vitro and to chromatin in cells when Parp1catalyzes PAR synthesis. We propose that poly-(ADP-ribosyl)ation of chromatin associated Parp1 serves as a novel mechanism for targeting a SNF2 family remodeler to chromatin. Using zebrafish as a model organism, we aimed to study possible roles of ALC1 in early organismal development. We found through qPCR and whole mount in situ analysis, that ALC1 is expressed ubiquitously within the blastomere prior to gastrulation, with peak expression observed during the Dome stage, and later at 24hpf that ALC1 is expressed within the anterior central nervous system. The injection of embryos with morpholinos targeting ALC1 resulted in pleiotropic phenotypes that were partially rescued by co-injection of either human or zebrafish mRNA. These findings suggest that Alc1 and its associated enzymatic activities are most likely required for proper organismal development.