Dimerization of CUL7 and PARC Is Not Required for All CUL7 Functions and Mouse Development

Abstract

CUL7, a recently identified member of the cullin family of E3 ubiquitin ligases, forms a unique SCF-like complex and is required for mouse embryonic development. To further investigate CUL7 function, we sought to identify CUL7 binding proteins. The p53-associated, parkin-like cytoplasmic protein (PARC), a homolog of CUL7, was identified as a CUL7-interacting protein by mass spectrometry. The heterodimerization of PARC and CUL7, as well as homodimerization of PARC and CUL7, was confirmed in vivo. To determine the biological role of PARC by itself and in conjunction with CUL7, a targeted deletion of Parc was created in the mouse. In contrast to the neonatal lethality of the Cul7 knockout mice, Parc knockout mice were born at the expected Mendelian ratios and exhibited no apparent phenotype. Additionally, Parc deletion did not appear to affect the stability or function of p53. These results suggest that PARC and CUL7 form an endogenous complex and that PARC and CUL7 functions are at least partially nonoverlapping. In addition, although PARC and p53 form a complex, the absence of effect of Parc deletion on p53 stability, localization, and function suggests that p53 binding to PARC may serve to control PARC function.

ACKNOWLEDGMENTS

We thank J. Horner and members of the DFCI Transgenic gene Targeting Core Facility for knockout mouse production; R. DePinho, N. Bardeesy, and A. Aguirre for the pKOII vector, EIIa-Cre mice, and general mouse advice; and E. McIntush at Bethyl Laboratories for help in antibody design and production. We also thank the Kazusa DNA Research Institute for KIAA clones, Darrell Borger for the pLB(N)CX T Ag construct, and J. Kasper for sharing unpublished data on CUL7.

J.R.S. was supported by an NSF Graduate Research Fellowship. This work was funded in part by National Cancer Institute grant RO1CA93804.