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Saitoh, Y., Miyagi, S., Ariga, H., Tsutsumi, K. (2002)
Functional domains involved in the interaction between Orc1 and transcriptional repressor AlF-C that bind to an origin/promotor of the rat aldlase B gene.
Nucleic Acids Res. 30: 5205-5212.
The promoter of the rat aldolase B (AldB) gene functions in vivo as an origin of DNA replication in the cells in which transcription of the gene is repressed. Previously, we identified two closely related DNA-binding proteins, AlF-C1 and AlF-C2, which repressed of the AldB gene promoter. We also reported that the binding site of these proteins, site C, is one of the necessarily required DNA elements of the AldB gene origin/promoter for autonomously replicating activity in transfected cells. In the present study, we show that AlF-C1 and AlF-C2 directly bind to Orc1, a subunit of the origin recognition complex (ORC). Deletion analyses revealed a functional domain in AlF-C2 for binding to Orc1, which located separately from the DNA-binding domain. In addition, we found a novel protein-interacting domain in Orc1 required for binding of AlF-C2, which was conserved in human, mouse and Chinese hamster, but not in Drosophila, flog and yeast. Thus, it is assumed that in mammalian cells, sequence-specific DNA binding proteins are involved in recruiting ORC to regulate replication initiation and/or transcription repression.

Wang, Y., Saitoh, Y., Hidaka, S., Sato, T., Tsutsumi, K. (2002)
Replication of plastid DNA.
Recent Res. Devel. Plant Biol. 2: 33-48.

Plastid is a name for organelles derived from a progenitor proplastid. The proplastid in immature cells of meristematic tissues differentiates with the host cells to various organelles including chloroplast, chromoplast, amyloplast, and leucoplast. Consequently, all these organelles contain the same genome DNA (plastid DNA, ptDNA). To maintain plastid lineages division of plastid and replication of ptDNA must take place. Recent reports showed that FtsZ and MinD, homologues of bacterial proteins required for cell division, play important roles in plastid division. In vivo and in vitro studies have mapped origins of ptDNA replication in several plant and algal species, and proposed at least two types of replication, D-loop-started unidirectional replication and rolling circle replication. These studies further suggested that replication initiation does not depend solely on the primary structure. Copy number of plastid and ptDNA varies depending on developmental stages and physiological status of host cells. These regulations might overlap those of initiation and made of replication.

Yoshino, M., Kanazawa, A., Tsutsumi, K., Nakamura, I., Takahashi, K., Shimamoto Y. (2002)
Structural Variation Around the Gene Encoding the ƒ¿ Subunit of Soybean ƒÀ-Conglycinin and Correlation with the Expression of the ƒ¿ Subunit.
Breeding Science 52: 285-292.

We have identified two genes, located approximately 2.5 kb apart in the soybean genome, that are closely related to the ƒ¿ subunit of ƒÀ-conglycinin. One of these genes has been shown to encode the ƒ¿ subunit and the other is very similar to the ƒ¿ subunit gene (referred to as the "ƒ¿-related gene"). To determine whether the latter ƒ¿-related gene expresses the ƒ¿ subunit, the structure of the chromosomal DNA region that contains the two genes was compared among soybean varieties exhibiting different expression levels of the subunit protein. We observed the presence of deletions of the ƒ¿ subunit and ƒ¿-related genes in some varieties. In the naturally occurring variety Keburi, which accumulates the ƒ¿ subunit protein, the entire ƒ¿-related gene was deleted in addition to the previously known deletion of the ƒ¿' subunit gene. On the contrary, the ƒ¿ subunit gene was deleted in Monshidou Gong 503 and Kari-kei 434. These structural analyses revealed that the ƒ¿-related gene expresses the ƒ¿ subunit at least in Moshidou Gong 503 and Kari-kei 434. These two varieties do not harbour the ƒ¿ subunit gene, but carry the intact ƒ¿-related genes and still express the ƒ¿ subunit.

Ejiri, S. (2002)
Moonlighting functions of polypeptide elongation factor 1: From actin bundling to zinc finger protein R1-associated nuclear localization.
Biosci. Biotech. Biochem. 66: 1-21.

@Eukaryotic polypeptide elongation factor EF-1 is not only a major translational factor, but also one of the most important multifunctional (moonlighting) proteins. EF-1 consists of four different subunits collectively termed EF-1ƒ¿ and EF-1ƒÀƒÀ'ƒÁ in plants and animals, respectively. EF-1ƒ¿EGTP catalyzes the binding of aminoacyl-tRNA to the A-site of the ribosome. EF-ƒÀƒÀ'ƒÁ (EF-1ƒÀ and EF-ƒÀ'), catalyzes GDP/GTP exchange on EF-1ƒ¿EGDP to regenerate EF-1ƒ¿EGTP. EF-1ƒÁ has recently been shown to have glutathione S-transferase activity. EF-2 catalyzes the translocation of peptidyl-tRNA from the A-site to the P-site on the ribosome. Recently, molecular mimicry among tRNA, elongation factors, releasing factor (RF), and ribosome recycling factor (RRF) has been demonstrated and greatly improved our understanding of the mechanism of translation.
@Moreover, eukaryotic elongation factors have been shown to be concerned or likely to be concerned in various important cellular processes or serious diseases, including translational control, signal transduction, cytoskeletal organization, apoptosis, adult atopic dermatitis, oncogenic transformation, nutrition, and nuclear processes such as RNA synthesis and mitosis.This article aims to overview the recent advances in protein biosynthesis, concentrating on the moonlighting functions of EF-1.

Kamiie, K., Nomura, Y., Kobayashi, S., Taira, H., Kobayashi, K., Matsuzawa, H., Yamashita, T., Kidou, S. and Ejiri, S. (2002)
Cloning and expression of silk gland elongation factor 1ƒÁ in Escherichia coli.
Biosci. Biotech. Biochem. 66: 558-565.

@Elongation factor 1 (EF-1) from the silk gland of Bombyx mori consists of ƒ¿-, ƒÀ-, ƒÀ'-, and ƒÁ-subunits. EF-1ƒ¿EGTP catalyzes the binding of aminoacyl- tRNA to ribosomes concomitant with the hydrolysis of GTP. EF-1ƒÀƒÀ'ƒÁ catalyzes the exchange of EF-1ƒ¿-bound GDP for exogenous GTP and stimulates the EF-1ƒ¿ -dependent binding of aminoacyl-tRNA to ribosomes.
@EF-1ƒÁ cDNA, which contains an open reading frame (ORF) encoding a polypeptide of 423 amino acid residues, was amplified and cloned by PCR from a silk gland cDNA library. The calculated molecular mass and predicted pI of the product were 48, 388 Da and 5.84, respectively. The silk gland EF-1ƒÁ shares 67.3“ amino acid identity with Artemia salina EF-1ƒÁ. The N-terminal domain (amino acid residues 1--211) of silk gland EF-1ƒÁ is 29.3“ identical to maize glutathione S-transferase. We demonstrated that silk gland EF-1ƒÁ bound to glutathione Sepharose, suggesting that the N-terminal domain of EF-1ƒÁ may have the capacity to bind to glutathione.

Kato, K., Kidou, S., Miura, H. and Sagawa, S. (2002)
Molecular cloning of the wheat CK2ƒ¿ gene and detection of its linkage with Vrn-A1 on chromosome 5A.
Theor. Appl. Genet. 104: 1071-1077.

The casein kinase CK2 is one of the major multifunctional protein kinases in cells that is expressed ubiquitously and is essential for survival. The ƒ¿- subunit of CK2 is thought to be involved in light-regulated gene expression and rhythmic expression of genes by circadian rhythm in plants. The rice chromosome-3 region containing the photoperiod-response Hd6 gene, an orthologue of the CK2ƒ¿genes of Arabidopsis and maize, is in synteny with the wheat chromosome-5A Vrn-A1 region. This evidence proposes two possibilities, first the wheat Vrn-A1 is an orthologue of the rice CK2ƒ¿, and second the wheat CK2ƒ¿which has not yet been identified is located independently but tightly linked to Vrn-A1. To clarify whether the wheat CK2ƒ¿gene is conserved in the Vrn-A1 region and to elucidate the above two possibilities, we attempted to isolate this gene from the wheat cDNA library and to map it on the chromosome-5A region that is syntenous to the rice Hd6 region. The isolated cDNA clone showed an extremely high homology with the Arabidopsis CK2ƒ¿gene. Using this clone as a probe genomic Southern-blot analyses of the aneuploid lines available in Chinese Spring assigned the wheat homologue of CK2ƒ¿to the long arm of chromosome 5A. Furthermore, a linkage analysis using an F2 population having recombination in the Vrn-A1 region revealed that the wheat CK2ƒ¿, designated as tck2a, is tightly linked to Vrn-A1 by 1.1 cM

Kawamura, Y. and M. Uemura (2002)
Changes in the plasma membrane from Arabidopsis thaliana within 1 week of cold acclimation.
In: Plant Cold Hardiness: Gene Regulation and Genetic Engineering, P.H. Li and E.T. Palva, eds., Plenum Press, New York, pp.181-194.

In the present study, we identified six groups of plasma membrane proteins that are changed during cold acclimation of Arabidopsis. Among those proteins, dehydrins and the proteins related to CO2 fixation, proteolysis or osmotic stress increased within only 1 day of cold acclimation and then continued to gradually increase over a period of 7 days of cold acclimation. On the other hand, the lipid composition of plasma membrane does not change substantially, at least after 1 day of cold acclimation. These results indicate that changes in the plasma membrane proteins occur more rapidly than those in the lipid composition during the process of cold acclimation. Some cold?induced plasma membrane proteins may be related to changes in the incidence of freeze-induced lesions associated with the plasma membrane in the early stage of cold acclimation.

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