title: A novel interaction between calreticulin and ubiquitin-like nuclear protein in rice.
abstract: Calreticulin (CRT), a major Ca2+ -sequestering protein, has been implicated in a variety of cellular functions such as Ca2+ storage, signaling and chaperone activity within the cytoplasm and endoplasmic reticulum. To investigate the biological role of CRT in rice, 21 partial cDNAs, encoding proteins that interacted with rice CRT in a yeast two-hybrid interaction-cloning system, were characterized and the nucleotide sequences were found to be identical to each other. A full-length cDNA of 3.5 kb, obtained from rice genomic sequence data and 5' RACE, codes for a novel protein of 966 amino acid residues and was designated as CRTintP (CRT interacting protein). Primary sequence analysis of CRTintP showed no sequence homology with the known functional proteins; however, a potential ubiquitin-like domain at the N-terminal together with a putative leucine zipper, a nuclear localization signal and several sites for serine/threonine kinases were evident. Cellular localization of CRTintP demonstrated its role in directing green fluorescent protein to the nucleus in onion epidermal cells. Northern and immunoblot analysis showed increased expression of CRT and CRTintP in response to cold stress. Co-immunoprecipitation using anti-CRT antibodies confirmed the existence of the CRT-CRTintP complex in vivo in the stressed leaf tissue, suggesting their potential role in regulating stress response.
authors.affiliation: Japan Society for the Promotion of Science, Tsukuba, Ibaraki, 305-8602 Japan.
authors.forename: Arun
authors.initials: A
authors.lastname: Sharma
authors.forename: Minako
authors.initials: M
authors.lastname: Isogai
authors.forename: Taichi
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Kengo
authors.initials: K
authors.lastname: Sakaguchi
authors.forename: Junji
authors.initials: J
authors.lastname: Hashimoto
authors.forename: Setsuko
authors.initials: S
authors.lastname: Komatsu
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000235:genetics; D000595:Amino Acid Sequence / Q000235:genetics; D001483:Base Sequence / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D037282:Calreticulin / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D003080:Cold Temperature / Q000009:adverse effects; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D019441:Plant Epidermis / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000235:genetics; D014452:Ubiquitins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D037282:Calreticulin; D018076:DNA, Complementary; D008164:Luminescent Proteins; D010940:Plant Proteins; D014452:Ubiquitins; D049452:Green Fluorescent Proteins