A split CandA regulates ubiquitin ligases in Aspergillus nidulans

Elke U . Schwier 1, Martin Christmann 1, Kerstin Helmstaedt1, Krystyna Nahlik 1, Mieke Westermann 2, Stephanie Grond 2, Silke Busch 1, Gerhard H. Braus 1

Author address: 

Georg-August-Universität Göttingen, 1Institut für Mikrobiologie und Genetik, 2Institut für Organische und Biomolekulare Chemie, Göttingen, Germany, [email protected]

Abstract: 

Cullins are a class of scaffold proteins, which are part of the SCF (Skp1/Cullin/F-box protein) ubiquitin ligases. The activity of these ligases is positively regulated by the neddylation of the cullin while binding of the cullin to Cand1 (cullin-associated Nedd8-dissociated protein 1) favors the disassembly and impairs the reassembly of the complex. Cand1 blocks the neddylation site in the C-terminal part of cullin as well as the Skp1 adaptor binding site in the N-terminal region of cullin. In Aspergillus nidulans, the gene encoding the putative homolog of Cand1 is split into two genes (candA-N and candA-C) encoding two proteins each with one cullin binding site. Deletion of either gene causes an impairment of the asexual cycle, a block of the sexual cycle and the production of brownish-red pigments. These defects can be complemented by a candA-N::C fusion construct. Both CandA proteins interact with each other, but only CandA-C associates with cullins in a yeast two-hybrid assay indicating that CandA-N binding to cullin is mediated by CandA-C. In vivo, CandA-N requires CandA-C for transport into the nucleus. Binding of only CandA-C to cullin might reflect transient states in the disassembly/reassembly cycle of SCF ubiquitin ligases which could be adopted independently of cullin deneddylation.
2009

abstract No: 

22

Full conference title: 

6th International Aspergillus Meeting
    • Asperfest 6 (2009)