Dynamic changes in nuclear import of a nuclear localisation signal-bearing substrate in 8-cell stage porcine embryos
Yanfang Li A , Ki-Eun Park A B and Ryan A. Cabot A CA Department of Animal Sciences, Purdue University, 915 W. State St., West Lafayette, IN 47907, USA.
B Present address: Department of Avian and Animal Sciences, University of Maryland, College Park, MD 20742, USA.
C Corresponding author. Email: rcabot@purdue.edu
Reproduction, Fertility and Development 27(2) 385-394 https://doi.org/10.1071/RD13205
Submitted: 28 June 2013 Accepted: 29 October 2013 Published: 17 December 2013
Abstract
Coordinated intracellular trafficking is critically important for proper timing of major cellular events during embryogenesis. Nuclear import mediated by the karyopherin α/β (importin α/β) heterodimer is perhaps the best characterised nuclear trafficking system in eukaryotic cells. Seven karyopherin α subtypes have been identified in the domestic pig, and although each karyopherin α subtype transports proteins bearing classical nuclear localisation signals (NLSs), individual karyopherin α subtypes have been shown to preferentially transport specific cargoes. The aim of the present study was to determine the mechanism by which BRN2, a transcription factor previously reported to be transported by the karyopherin α/β heterodimer, gains access to the nucleus in porcine oocytes and embryos. Using a combination of in vivo and in vitro assays, we tested the hypothesis that discrete karyopherin α subtypes transport BRN2 into the nuclei of porcine oocytes and cleavage stage embryos. Our results show that ectopically expressed BRN2 adopts a nuclear localisation in all nuclei through the 4-cell stage of development, whereas only a subset of blastomeres in 8-cell stage embryos possess nuclear BRN2. This pattern is unique to BRN2 because another ectopically expressed NLS-containing protein is able to adopt a nuclear localisation in all blastomeres of 8-cell stage embryos.
Additional keywords: BRN2, karyopherin, NLS, trafficking.
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