Genetic and molecular characterization of Roc-Cullin interactions in Drosophila melanogaster E3 ubiquitin ligases

Genetic and molecular characterization of Roc-Cullin interactions in Drosophila melanogaster E3 ubiquitin ligases Public Deposited

Last Modified

Creator

Reynolds, Patrick J.
- Affiliation: College of Arts and Sciences, Department of Biology

Abstract

Cullin-dependent E3 ubiquitin ligases (CDL) are key regulators of protein destruction that participate in a wide range of cell biological processes. The Roc subunit of CDL contains an evolutionarily conserved RING domain that recruits ubiquitin charged E2 and is essential for ubiquitylation. Drosophila melanogaster contains three highly related Roc proteins: Roc1a, Roc1b, and Roc2. We previously reported that mutation of Roc1a and Roc1b causes lethality and male sterility, respectively. Here we show that these disparate phenotypes are partially due to the ability of the Rocs to bind specific Cullins. Roc1a binds Cul1-4, Roc1b binds Cul3, and Roc2 binds Cul5. Through domain swapping experiments, we demonstrate that specific Cullin binding is strongly influenced by the Roc NH2-terminal domain, which forms an inter-molecular β-sheet with the Cullin. Substitution of the Roc1a RING domain with that of Roc1b results in a protein with similar Cullin binding properties to Roc1a but that cannot complement Roc1a mutant lethality, indicating that the identity of the RING domain is an important determinant of CDL function as well. We also identified null mutations of Roc2 and Cul5 and show that they cause no overt developmental phenotype, consistent with our observation that Roc2 and Cul5 proteins are exclusive binding partners.

Date of publication