Regulation of Nuclear Transport Factor by Port-Translational Modification

Mohd, Khamsah Suryati and Clarke, Paul (2012) Regulation of Nuclear Transport Factor by Port-Translational Modification. In: Malaysia Society of Applie Biology Annual Seminar, Kuala Terengganu.

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In eukaryotic cells, molecules need to be transported selectively and efficiently between the cytoplasm and nucleus. Although the fundamental mechanism of nucleocytoplasmic transport is generally established, the issue on whether or how the transport machinery is regulated in relation to the cell cycle remains elusive. This work examined the posibility of the regulation of nucleocytoplasmic transport by post-translational modification of transport factors. The phosphorylation of a nuclear transport factor, namely importin alpha was examined. Immunoblotting of HeLa and U2OS cell lysates indicated that nuclear import adaptor, importin alpha is upregulated in mitosis. Importin alpha consists of seven isoforms. In knockdown experiment by siRNA technology followed by Phos-tag™ SDS-PAGE and western blotting, it was found that the most abundant isoform, importin α1 is phosphorylated in mitosis. Through site directed mutagenesis, it revealed that importin alpha 1 is phosphorylated at two sites; threonine 9 and serine 62. The phosphorylation of both sites as blocked by CDK1 inhibitors in cells and in vitro, and purified CDK1/cyclin B1 able to phosphorylated importin alpha 1 in vitro, indicating that CDK1/cycB1 is the kinase responsible for importin alpha 1 phosphorylation. Finding from this study have provided important leads that phosphorylation may play a role in the interaction between importin alpha 1 and its binding partner and its transport cargo. This regulation may be different from other alpha isoform as not all isoforms are phosphorylated in cells. This is very intriguing findings as another level of regulation was revealed in already tightly regulated and signal-mediated nuclear transport, particularly on the specificity of nuclear import adaptor, importin alpha and its associates in cell cycle dependent manner.

Item Type: Conference or Workshop Item (Speech)
Subjects: R Medicine > RM Therapeutics. Pharmacology
Faculty / Institute: Faculty of Bioresources & Food Industry
Depositing User: Dr Khamsah Suryati Mohd
Date Deposited: 13 Jan 2015 08:47
Last Modified: 13 Jan 2015 08:47

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