The Use of RUVBL1‐2 in the Oncogenic Process

Abstract

RUVBL1 and RUVBL2 are two highly conserved eukaryotic AAA+ (ATPases Associated with diverse cellular Activities) proteins that engage in a diverse array of cellular functions. These functions can range from ribonucleoprotein complex assembly and cellular transformation to chromatin remodeling and DNA damage response. Individually, RUVBL1 and RUVBL2 form homohexamers with weak ATPase activities. However, together they form highly active heterohexameric or dodecameric complexes made up of alternating units of RUVBL1 and RUVBL2. Like all other AAA+ proteins, RUVBL1 and RUVBL2 ATPases contain a Walker A and a Walker B motif. These motifs are required for nucleotide binding and hydrolysis, respectively. RUVBL1 and RUVBL2 are each made up of three distinct domains: an N terminal αβα subdomain of the AAA+ domain, a 170 amino-acid insertion domain, and an all α subdomain of the AAA+ domain. The amino-acid insertion domain is unique to RUVBL1 and RUVBL2 and can mediate DNA or RNA binding. Despite its many essential functions, the complex of RUVBL1 and RUVBL2 (referred to as RUVBL1/2 here) is present at low levels in eukaryotic cells. It is therefore thought that RUVBL1/2 interacts only transiently with its binding partners and acts as a chaperone for assembly of other complexes. The molecular mechanism by which the RUVBL1/2 ATPase engages in cellular activities remains elusive. Interestingly, RUVBL1/2 is overexpressed in numerous human cancers including gastric, bladder, pancreatic, and breast cancers. For example, researchers have found that in pancreatic ductal adenocarcinoma (PDAC), which is among the deadliest cancers, RUVBL1 helps the formation of membrane protrusions by promoting actin polymerization. These protrusions increase the invasiveness and metastatic properties of PDAC cells. Due to their strong link to oncogenesis, design of inhibitors against RUVBL1/2 is a major area of research. Although members of the AAA+ family are challenging drug targets, recent high-resolution structures and new drug screening strategies have enabled advances in design of novel AAA+ inhibitors. For example, the small molecules Sorafenib and CB-6644 were recently reported to inhibit the ATPase activity of the RUVBL1/2 complex. With further optimizations and testing, these drugs may be improved and potentially considered as potent therapeutic inhibitors of RUVBL1/2 activity. The Walton SMART team has designed a 3D model of RUVBL1/2 to investigate the relationship between the molecular structure and function of this ATPase complex.