Regular article
Characterization of two subunits of Arabidopsis 19S proteasome regulatory complex and its possible interaction with the COP9 complex1

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Abstract

The nuclear localized, multi-subunit COP9 complex (or COP9 signalosome) is a key developmental modulator involved in repression of photomorphogenesis. In an effort to further define the molecular actions of the COP9 complex, a yeast two hybrid interactive screen was undertaken to identify proteins that could directly interact with one subunit of this complex, namely FUS6/COP11. This screen identified one specific interactive protein, AtS9, that is likely the Arabidopsis non-ATPase S9 (subunit 9) of the 19S regulatory complex from the 26S proteasome. AtS9 specifically interacts with FUS6/COP11 via the C-terminal domain of FUS6/COP11, which is distinct from the N-terminal domain necessary for FUS6/COP11 to interact with itself. As anticipated, AtS9 is not a member of the COP9 complex, but tightly associates with an ATPase subunit of the Arabidopsis 19S proteasome regulatory complex, AtS6A. Since all three proteins, FUS6/COP11, AtS9, and AtS6A, are present as complexed forms in vivo, the observed interaction implies that the COP9 complex may directly interact with the 19S regulatory complex of the 26S proteasome or other potential AtS9-containing complex. This notion is consistent with the parallel tissue-specific expression patterns and the similar, predominantly nuclear localization of both the COP9 complex and the AtS9 protein.

Keywords

Arabidopsis
COP9
protein degradation
proteasome
photomorphogenesis

Abbreviations

eIF3
eukaryotic translation initiation factor 3
AtS9
Arabidopsis 19S proteosome regulatory complex subunit 9
HTH
helix-turn-helix
ORF
open reading frame
EST
expressed sequence tag
AAA
ATPases associated with diverse activation
DAP1
4′-6-diamidino-2-phenylindole
BAC
bacterial artificial chromosome
YAC
yeast artificial chromosome
HIV
human immunodeficiency virus
pfu
plaque forming units

Cited by (0)

1

Edited by J. Karn

2

S. F. Kwok and J. M. Staub contributed equally to this work.

3

Present address: J. M. Staub, Monsanto Company, 700 Chesterfield Parkway North, Mail Code BB3G, St. Louis, MO 63017, USA.