Nuclear localization of Chfr is crucial for its checkpoint function

• Published in: Molecules and cells Vol. 27; no. 3; pp. 359 - 363
• Main Authors: Kwon, Y.E. (Seoul National University, Seoul, Republic of Korea), Kim, Y.S. (Seoul National University, Seoul, Republic of Korea), Oh, Y.M. (Seoul National University, Seoul, Republic of Korea), Seol, J.H. (Seoul National University, Seoul, Republic of Korea), E-mail: jhseol@snu.ac.kr
• Format: Journal Article
• Language: English
• Published: Springer Korean Society for Molecular and Cellular Biology 01.03.2009; 한국분자세포생물학회
• Subjects: Amino Acid Sequence; Biochemistry; Biomedical and Life Sciences; Biomedicine; Biotechnology; Cell Biology; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Cell Line; Cell Nucleus - metabolism; CELLS; CELLULE; CELULAS; Chfr; Fluorescent Antibody Technique; HeLa Cells; Humans; Life Sciences; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; nuclear localization signal (NLS) sequence; Nuclear Localization Signals - genetics; Nuclear Localization Signals - metabolism; Poly-ADP-Ribose Binding Proteins; Transfection; Ub-ligase; Ubiquitin-Protein Ligases - genetics; Ubiquitin-Protein Ligases - metabolism; ubiquitination; 생물학; Chfr; ubiquitination; Ub-ligase; nuclear localization signal (NLS) sequence
• ISSN: 1016-8478; 0219-1032
• DOI: 10.1007/s10059-009-0046-7

Chfr, a checkpoint with FHA and RING finger domains, plays an important role in cell cycle progression and tumor suppression. Chfr possesses the E3 ubiquitin ligase activity and stimulates the formation of polyubiquitin chains by Ub-conjugating enzymes, and induces the proteasome-dependent degradation of a number of cellular proteins, including Plk1 and Aurora A. While Chfr is a nuclear protein that functions within the cell nucleus, how Chfr is localized in the nucleus has not been clearly demonstrated. Here, we show that nuclear localization of Chfr is mediated by nuclear localization signal (NLS) sequences. To reveal the signal sequences responsible for nuclear localization, a short lysine-rich stretch (KKK) at amino acid residues 257-259 was replaced with alanine, which completely abolished nuclear localization. Moreover, we show that nuclear localization of Chfr is essential for its checkpoint function but not for its stability. Thus, our results suggest that NLS-mediated nuclear localization of Chfr leads to its accumulation within the nucleus, which may be important in the regulation of Chfr activation and Chfr-mediated cellular processes, including cell cycle progression and tumor suppression.