Poster: Cell Cycle

Abs # 238: Structure, expression and sequence-specific DNA binding properties of tobacco telomeric protein NgTBP1

Presenter:	Yang, Seong Wook , YahnYatz@korea.com
Additional Authors	Lee, Jai-Jin  (A)   Kim, Dong-Hyun  (A)   Lee, Jai-Hyeok  (A)   Kim, Yun Ju  (A)   Chon, Yoon Joo  (A)   Kim, Seong Gun  (A)   Kim, Woo Teak  (A)
Affiliations:	(A): Department of Biology, College of Science, Yonsei University

Plant telomeres that consist of tandem array of short sequence (TTTAGGG) are specifically bound by telomere binding proteins (TBPs). Here we report the characterization of a gene (NgTBP1), encoding a telomeric repeat binding protein, which was isolated from Nicotiana glutinosa L. The 75 kDa protein possesses a single Myb-like DNA binding motif at the C-terminal region with extensive homology to Myb-like domain found in plant TBPs, such as RTBP1, AtTRP1, OsTBP1 and AtTRP1ho. We used gel retardation assay to define the binding site of isolated NgTBP. The C-terminal 110 residues, including Myb-like domain, were sufficient for binding to the telomeric sequence. The Myb-like domain of NgTBP was able to recognize internal GGGTTT sequence in the two-telomere repeats as a binding center and that its DNA binding mode was very similar to that of RTBP1. Also, The NgTBP was capable of sequence-specific DNA binding as a homodimer. Most of nuclear proteins and TBPs carry a nuclear localization signal (NLS) motif. To define nuclear localization of NgTBP, we made GFP-NgTBP fusion protein and introduced into onion cells. The GFP-NgTBP was efficiently transported to the onion nucleus. Human Pin2 is shown to be highly regulated during the cell cycle. However, nothing is known about TBP function and regulation during the cell cycle in the plant system. The NgTBP gene is expressed in several tissues as old leaf, stem, old root and in the stationary phase of suspension cell culture where the most of tissue and BY-2 cells are quiescent in the G phase without telomerase activity.