A novel interaction between calreticulin and ubiquitin-like nuclear protein in rice

• Published in: Plant and cell physiology Vol. 45; no. 6; pp. 684 - 692
• Main Authors: Sharma, A. (National Inst. of Agrobiological Sciences, Tsukuba, Ibaraki (Japan)), Isogai, M, Yamamoto, T, Sakaguchi, K, Hashimoto, J, Komatsu, S
• Format: Journal Article
• Language: English
• Published: Japan Oxford University Press 01-06-2004; Oxford Publishing Limited (England)
• Subjects: Active Transport, Cell Nucleus - genetics; Amino Acid Sequence - genetics; Base Sequence - genetics; Binding Sites - genetics; BiP; CALCIUM BINDING PROTEINS; calreticulin; Calreticulin - genetics; Calreticulin - metabolism; calreticulin-interacting protein; Cell Nucleus - genetics; Cell Nucleus - metabolism; Cold Temperature - adverse effects; CRT; CRTintP; CYTOLOGY; DNA, Complementary - analysis; DNA, Complementary - genetics; endoplasmic reticulum; Gene Expression Regulation, Plant - genetics; GFP; green fluorescent protein; Green Fluorescent Proteins; Keywords: Calreticulin — CRTintP — Rice — Stress response; lumenal binding protein; Luminescent Proteins - metabolism; Molecular Sequence Data; NUCLEOTIDE SEQUENCE; Oryza - genetics; Oryza - metabolism; ORYZA SATIVA; Plant Epidermis - metabolism; Plant Proteins - genetics; Plant Proteins - isolation & purification; Plant Proteins - metabolism; PROTEIN METABOLISM; Protein Structure, Tertiary - genetics; STRESS; ubiquitin-like domain; Ubiquitins - genetics; Ubiquitins - isolation & purification; Ubiquitins - metabolism; UbL
• ISSN: 0032-0781; 1471-9053
• DOI: 10.1093/pcp/pch077

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 ubiquitinlike 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.