The COP9 Complex, a Novel Multisubunit Nuclear Regulator Involved in Light Control of a Plant Developmental Switch

Abstract

Arabidopsis COP9 is a component of a large protein complex that is essential for the light control of a developmental switch and whose conformation or size is modulated by light. The complex is acidic, binds heparin, and is localized within the nucleus. Biochemical purification of the complex to near homogeneity revealed that it contains 12 distinct subunits. One of the other subunits is COP11, mutations in which result in a phenotype identical to cop9 mutants. The COP9 complex may act to regulate the nuclear abundance of COP1, an established repressor of photomorphogenic development. During the biogenesis of the COP9 complex, a certain degree of prior subunit association is a prerequisite for proper nuclear translocation. Since both COP9 and COP11 have closely related human counterparts, the COP9 complex probably represents a conserved developmental regulator in higher eukaryotes.

The p44S10 locus, encoding a subunit of the proteasome regulatory particle, is amplified during progression of cutaneous malignant melanoma

“…fus6/cop11 is found in a large multiprotein complex with cop9 and functions in lightmediated signaling and transcriptional regulation (Chamovitz et al, 1996). This cop9 complex or`signalosome' is highly conserved in mammalian cells, possesses multiple subunits with similarity to the proteasome regulatory particle, and exhibits kinase activity for proteasome-regulated proteins including NFkB, IkBa, and the amino-terminal activation domain of c-Jun (Seeger et al, 1998).…”

Characterization of theVIER F-BOX PROTEINEGenes fromArabidopsisReveals Their Importance for Plant Growth and Development

“…Arabidopsis csn mutants are characterized by their constitutive photomorphogenic phenotype, which includes loss of skotomorphogenic growth, chloroplast differentiation, and the expression of light-induced genes in dark-grown seedlings (Chamovitz et al, 1996;Kwok et al, 1996). The seedling-lethal csn mutants also fail to develop a proper root and lateral roots.…”

Arabidopsis Homologs of a c-Jun Coactivator Are Present Both in Monomeric Form and in the COP9 Complex, and Their Abundance Is Differentially Affected by the Pleiotropic cop/det/fus Mutations

“…Cloning and molecular studies of COP9 indicate that it encodes a protein exclusively present in a high molecular weight, nuclear-localized protein complex known as the COP9 complex (Wei et al, 1994b). Biochemical purification of the COP9 complex revealed that it is multisubunit in nature, with a total molecular mass of ‫ف‬ 550 kD (Chamovitz et al, 1996). Interestingly, initial studies of two mutants in the pleiotropic cop / det / fus collection, fus6 (also called cop11 ) and cop8 , indicate that the COP9 complex is unstable in these mutants (Wei et al, 1994b).…”