title: Intrinsic protein-protein interaction-mediated and chaperonin-assisted sequential assembly of stable bardet-biedl syndrome protein complex, the BBSome.
abstract: The pleiotropic features of obesity, retinal degeneration, polydactyly, kidney abnormalities, cognitive impairment, hypertension, and diabetes found in Bardet-Biedl syndrome (BBS) make this disorder an important model disorder for identifying molecular mechanisms involved in common human diseases. To date, 16 BBS genes have been reported, seven of which (BBS1, 2, 4, 5, 7, 8, and 9) code for proteins that form a complex known as the BBSome. The function of the BBSome involves ciliary membrane biogenesis. Three additional BBS genes (BBS6, BBS10, and BBS12) have homology to type II chaperonins and interact with CCT/TRiC proteins and BBS7 to form a complex termed the BBS-chaperonin complex. This complex is required for BBSome assembly. Little is known about the process and the regulation of BBSome formation. We utilized point mutations and null alleles of BBS proteins to disrupt assembly of the BBSome leading to the accumulation of BBSome assembly intermediates. By characterizing BBSome assembly intermediates, we show that the BBS-chaperonin complex plays a role in BBS7 stability. BBS7 interacts with BBS2 and becomes part of a BBS7-BBS2-BBS9 assembly intermediate referred to as the BBSome core complex because it forms the core of the BBSome. BBS1, BBS5, BBS8, and finally BBS4 are added to the BBSome core to form the complete BBSome.
authors.affiliation: Department of Pediatrics, Division of Medical Genetics and Howard Hughes Medical Institute, University of Iowa, Iowa City 52242, USA.
authors.forename: Qihong
authors.initials: Q
authors.lastname: Zhang
authors.forename: Dahai
authors.initials: D
authors.lastname: Yu
authors.forename: Seongjin
authors.initials: S
authors.lastname: Seo
authors.forename: Edwin M
authors.initials: EM
authors.lastname: Stone
authors.forename: Val C
authors.initials: VC
authors.lastname: Sheffield
mesh_terms: D000818:Animals; D020788:Bardet-Biedl Syndrome / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D005260:Female; D056385:Group II Chaperonins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation
chemical_list: D008869:Microtubule-Associated Proteins; D046912:Multiprotein Complexes; D056385:Group II Chaperonins