Investigation of the regulation of nuclear translocation of the transcription factor mesoderm induction-early response 1 (mi-er1) during embryonic development of Xenopus laevis

Post, Janine Nicole (2002) Investigation of the regulation of nuclear translocation of the transcription factor mesoderm induction-early response 1 (mi-er1) during embryonic development of Xenopus laevis. Doctoral (PhD) thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (33MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

Temporal and spatial regulation of nuclear transport of transcription factors is important for regulating the function of many cellular and developmental processes. Here the regulation of nuclear transport of a Xenopus transcription factor, mesoderm induction-early response 1, MI-ER1, was investigated. -- It was shown that MI-ER1 is actively transported to the cell nuclei of transfected NIH 3T3 cells as well as in Xenopus embryos. The active import of MI-ER1 into the cell nuclei is dependent on the presence of an intact nuclear localization signal (NLS) located in the C-terminus of the protein. The core of this NLS consists of amino acids ⁴⁶³RPIKRQRMD⁴⁷¹ but we show that addition of amino acids flanking this region results in more efficient import into the cell nuclei. It was also shown that an additional, albeit weak, NLS is present in the N-terminus of MI-ER1. -- During embryonic development in Xenopus laevis MI-ER1 is localized in the cytoplasm by cytoplasmic retention, but localizes to the nucleus during the mid-blastula stages. Investigation into the regulation of cytoplasmic retention of MI-ER1 in Xenopus laevis embryos, showed that the NLS (ER457-475) of Ml-ER1 is able to direct β-GAL to the nucleus prematurely, which suggests that cytoplasmic retention of MI-ER1 is not dependent on NLS recognition and binding by the import machinery. -- Investigation of a phosphorylation site in the vicinity of this NLS shows, that the regulation of nuclear transport of MI-ER1 in Xenopus laevis is not regulated by phosphorylation of this cdc2 kinase/ PKA site. Furthermore, it is shown that cytoplasmic retention of MI-ER1 in embryos appears to be regulated by binding of MI-ER1 to an "anchor" molecule in the cytoplasm. It was shown that the region important for cytoplasmic retention is localized between amino acid residues 1 and 282.

Actions (login required)

View Item