SUNDAY, DECEMBER 4- Late Abstracts 1 - Molecular Biology of the ...

SUNDAY
transport system inside the chloroplast similar to the transport mechanism that exists between
the ER and the Golgi. CPSAR1 has a role in thylakoid biogenesis and in vesicle budding from
the inner envelope membrane for fusion with the thylakoids. As this mechanism is similar to the
cytosolic vesicular transport, a putative model is proposed in which the CPSAR1 need other
protein partners for the vesicular formation and transport. For this purpose we are using coimmunoprecipitation
and yeast-2-hybrid for identification of protein-protein interaction involving
CPSAR1. Ongoing bioinformatic studies of common motifs important for interactions and cargos
of the secretory pathway gives that they also exist for chloroplast localized proteins i.e. possible
protein interactors to the chloroplast vesicle traffic system. In addition, we are studying the
intraplastidial role of CPSAR1 from isolated chloroplast envelopes in vitro.
1995
A Novel Function of AWP1/ZFAND6: Regulation of Pex5p Export by Interacting with Cysmonoubiquitinated
Pex5p and AAA ATPase, Pex6p.
N. Miyata 1 , K. Okumoto 1,2 , S. Mukai 1 , M. Noguchi 2 , Y. Fujiki 1,3 ; 1 Department of Biology, Faculty
of Sciences, Kyushu University, Fukuoka, Japan, 2 Graduate School of Systems Life Sciences,
Kyushu University, Fukuoka, Japan, 3 JST, CREST, Tokyo, Japan
In biogenesis of peroxisome, a subcellular organelle, Pex5p is the shuttling receptor for
peroxisomal matrix proteins harboring peroxisome-targeting signal 1 (PTS1). Several peroxins
are involved in the Pex5p shuttling between the cytosol and peroxisomes. However, the precise
mechanism underlying the PTS1 receptor shuttling remains elusive. We herein suggest that
liver cytosol contains at least two distinct factors involved in the Pex5p export. We isolate one of
the factors by biochemical fractionation and in vitro Pex5p export assay and identify it as
AWP1/ZFAND6 (termed p40), a ubiquitin-binding NF-κB modulator. In in vitro Pex5p export
assay, recombinant p40, stimulates Pex5p export, whilst anti-p40 antibody interferes with Pex5p
export. p40 interacts with AAA ATPase Pex6p, but not Pex1p-Pex6p complex. p40 binds Cysubiquitinated
form of Pex5p more preferentially than unmodified Pex5p, apparently via its A20
zinc-finger domain. RNA interference for p40 significantly affects the PTS1 protein import into
peroxisomes. Furthermore, in the p40 knocked-down cells Pex5p is unstable, as in fibroblasts
from patients each defective in Pex1p, Pex6p, and Pex26p, all prerequisite to the Pex5p export.
Taken together, p40 is a novel cofactor of Pex6p involved in the regulation of Pex5p export in
peroxisome biogenesis.
1996
Docosahexaenoic acid is required for peroxisomal elongation, a prerequisite for division
of peroxisomes.
A. Itoyama 1 , M. Honsho 2 , Y. Abe 2 , Y. Yoshida 2 , Y. Fujiki 2,3 ; 1 Graduate School of Systems Life
Sciences, Kyushu University, Fukuoka, Japan, 2 Department of Biology, Faculty of Sciences,
Kyushu University, Fukuoka, Japan, 3 CREST, JST, Tokyo, Japan
Peroxisomal division is strictly regulated by several fission factors and cellular environments. In
the past decade, metabolic control of peroxisomal morphogenesis is postulated but remains
largely undefined. We herein identify docosahexaenoic acid (DHA, C22:6n-3) as the regulator of
the peroxisomal morphogenesis. Peroxisomes are much less abundant in fibroblasts from
patients defective in peroxisomal fatty-acid β-oxidation. Supplementation of DHA to such
fibroblasts induces proliferation of peroxisomes up to the same level in normal fibroblasts. DHAinducible
peroxisomal proliferation is abrogated upon treatment with dynamin-like protein 1
siRNA, suggesting the DHA-induced division of peroxisomes. DHA-induced peroxisomal
division is initiated by elongation of peroxisomes in a Pex11p-dependent manner. Furthermore,
DHA augments hyper-oligomerization of Pex11pβ, giving rise to Pex11pβ-enriched regions on