COMMD Proteins, a Novel Family of Structural and Functional Homologs of MURR1

Ezra Burstein,Jamie E Hoberg,Amanda S Wilkinson,Julie M Rumble,Rebecca A Csomos,Christine M Komarck,Gabriel N Maine,John C Wilkinson,Marty W Mayo,Colin S Duckett

doi:10.1074/jbc.m501928200

Abstract

MURR1 is a multifunctional protein that inhibits nuclear factor kappaB (NF-kappaB), a transcription factor with pleiotropic functions affecting innate and adaptive immunity, apoptosis, cell cycle regulation, and oncogenesis. Here we report the discovery of a new family of proteins with homology to MURR1. These proteins form multimeric complexes and were identified in a biochemical screen for MURR1-associated factors. The family is defined by the presence of a conserved and unique motif termed the COMM (copper metabolism gene MURR1) domain, which functions as an interface for protein-protein interactions. Like MURR1, several of these factors also associate with and inhibit NF-kappaB. The proteins designated as COMMD or COMM domain containing 1-10 are extensively conserved in multicellular eukaryotic organisms and define a novel family of structural and functional homologs of MURR1. The prototype of this family, MURR1/COMMD1, suppresses NF-kappaB not by affecting nuclear translocation or binding of NF-kappaB to cognate motifs; rather, it functions in the nucleus by affecting the association of NF-kappaB with chromatin.

Highlights

MURR1 is a multifunctional protein that inhibits nuclear factor ␬B (NF-␬B), a transcription factor with pleiotropic functions affecting innate and adaptive immunity, apoptosis, cell cycle regulation, and oncogenesis
Plasmids—The plasmids pEBB, pEBG, pEBB-MURR1-Flag and pEBB-MURR1-glutathione Stransferase (GST), pEBB-T7-I␬B-␣S.D., 2␬B-luc, and EGFP-p65 have been described previously [17,18,19,20,21,22]. pEBB-COMMD1-GST vectors expressing exon 1, exon 2-3, and exon 1-3 were generated by PCR amplification using pEBB-MURR1-Flag as template with the boundaries outlined in Fig. 3C. pEBB-MURR1-TAP was constructed by subcloning MURR1 into pEBB-TAP, which was generated by PCR amplification of the coding sequence for the tandem affinity purification (TAP) tag using pBS1539 as template [23]
MURR1 in fusion with the TAP affinity tag was transiently expressed in 293 cells, and MURR1-TAP was subsequently purified from cells lysates using two sequential chromatography columns containing IgG and calmodulin beads, respectively (Fig. 1A)

Summary

THE JOURNAL OF BIOLOGICAL CHEMISTRY

Vol 280, No 23, Issue of June 10, pp. 22222–22232, 2005 Printed in U.S.A. COMMD Proteins, a Novel Family of Structural and Functional Homologs of MURR1*□S. The proteins designated as COMMD or COMM domain containing 1–10 are extensively conserved in multicellular eukaryotic organisms and define a novel family of structural and functional homologs of MURR1. The prototype of this family, MURR1/COMMD1, suppresses NF-␬B not by affecting nuclear translocation or binding of NF-␬B to cognate motifs; rather, it functions in the nucleus by affecting the association of NF-␬B with chromatin. We report the discovery of a family of proteins structurally and functionally related to MURR1 These factors contain a unique and defining domain termed the COMM (copper metabolism gene MURR1) domain, and these proteins have been named COMM domain-containing or COMMD proteins. This work identifies a novel family of factors that regulate NF-␬B-mediated transcription by controlling the occupancy of NF-␬B on chromatin

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION