Poster: Cell Cycle & Cytokinesis

Abs # 1086: Regulation of biosynthesis and intracellular localization of rice and tobacco homologues of nucleosome assembly protein 1

Presenter:	Dong, Aiwu , awdong1970@yahoo.com
Authors	Dong, Aiwu  (A) (B)  Zhu, Yan  (A)   Yu, Yu  (A)   Shen, Wen-Hui  (B)
Affiliations:	(A): Department of Biochemistry, School of Life Sciences, Fudan University, Shanghai 200433, PR China (B): IBMP-CNRS, Universit?Louis Pasteur de Strasbourg, 12 rue du G閚閞al Zimmer, 67084 Strasbourg C閐ex, France

The nucleosome assembly protein 1 (NAP1) is considered as a conserved histone chaperone facilitating the assembly of nucleosomes in all eukaryotes. However, studies in yeast and animal celles also revealed that the NAP1 have diverse functions likely independent from nucleosome assembly activity. Here, we describe the isolation and characterization of cDNAs encoding NAP1-like proteins from the monocotyledon rice and the dicotyledon tobacco. Northern-blot analysis demonstrated that the two rice NAP1-like genes are predominantly expressed in stem tissues such as root and shoot apical meristems as well as in young flowers. During the cell cycle, all four tobacco NAP1-like genes are highly expressed, with one of them showing a slightly increased expression at G1/S transition. These results are consistent with a role for plant NAP1-like proteins in cell division. In vitro binding assays revealed that different NAP1-like proteins bind, with distinct relative binding strengths, to different classes of histones. Intracellular localization analyses showed that some NAP1-like proteins could be targeted into the nucleus whereas some others are exclusively cytoplasm-localized. It is thus likely that different plant NAP1-like proteins play distinct in vivo functions. Plant NAP1-like proteins were observed to concentrate around the metaphase plate and in the phragmoplast, suggesting a role for NAP1-like proteins in mitotic events and cytokinesis.