Intact structure of EGAM1 homeoproteins and basic amino acid residues in the common homeodomain of EGAM1 and EGAM1C contribute to their nuclear localization in mouse embryonic stem cells
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- 作者：Sho Sato ; Sanae Morita ; Momoe Iha ; Yuki Mori ; Saiko Sugawara ; Kano Kasuga ; Ikuo Kojima ; Noriaki Ozaki ; Hajime Muraguchi ; Keiju Okano ; Jun Iwashita ; Jun Murata ; Masahiro Hosaka ; Masayuki Kobayashi ; makoba@akita-pu.ac.jp
- 关键词：Crxos1 ; Egam1 ; Embryonic stem cells ; Homeoprotein ; Nuclear localization signal
- 刊名：Journal of Bioscience and Bioengineering
- 出版年：2013
- 出版时间：August, 2013
- 年：2013
- 卷：116
- 期：2
- 页码：141-146
- 全文大小：772 K
文摘
Recently, we identified the structurally related homeoproteins EGAM1, EGAM1N, and EGAM1C in both preimplantation mouse embryos and mouse embryonic stem (ES) cells. These EGAM1 homeoproteins act as positive or negative regulators of differentiation and cell growth in mouse ES cells, such that these proteins are considered transcriptional regulators. In this study, we investigated their nuclear localization and identified the amino acid residues crucial for the nuclear translocation of EGAM1 and EGAM1C. When expressed exogenously in pluripotent ES cells and somatic NIH3T3 cells, all EGAM1 homeoproteins localized to the nucleus. Analysis using the web-based tool PSORTII predicted a potential nuclear localization signal (NLS) motif, RKDLIRSWFITQRHR, in the homeodomain shared by EGAM1 and EGAM1C. The introduction of mutations, such as mutations from K or R, both basic amino acid residues, to A, in this potential NLS resulted in significant impairment of the nuclear localization of both EGAM1 and EGAM1C. In contrast, GFP fusion proteins of all the full-length EGAM1 homeoproteins failed to localize to the nucleus. These results, when taken together, suggest that basic amino acid residues in the common homeodomain of EGAM1 and EGAM1C and the intact structures of the EGAM1 homeoproteins contribute, at least in part, to the nuclear localization of these proteins in mouse ES cells.