Nuclear transporter Importin-13 plays a key role in the oxidative stress transcriptional response

K A Gajewska,H Lescesen,M Ramialison,K M Wagstaff,D A Jans

doi:10.1038/s41467-021-26125-x

K A Gajewska, H Lescesen + Show 3 more

Open Access

https://doi.org/10.1038/s41467-021-26125-x

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Abstract

The importin superfamily member Importin-13 is a bidirectional nuclear transporter. To delineate its functional roles, we performed transcriptomic analysis on wild-type and Importin-13-knockout mouse embryonic stem cells, revealing enrichment of differentially expressed genes involved in stress responses and apoptosis regulation. De novo promoter motif analysis on 277 Importin-13-dependent genes responsive to oxidative stress revealed an enrichment of motifs aligned to consensus sites for the transcription factors specificity protein 1, SP1, or Kruppel like factor 4, KLF4. Analysis of embryonic stem cells subjected to oxidative stress revealed that Importin-13-knockout cells were more resistant, with knockdown of SP1 or KLF4 helping protect wild-type embryonic stem cells against stress-induced death. Importin-13 was revealed to bind to SP1 and KLF4 in a cellular context, with a key role in oxidative stress-dependent nuclear export of both transcription factors. The results are integral to understanding stress biology, highlighting the importance of Importin-13 in the stress response.

Highlights

The importin superfamily member Importin-13 is a bidirectional nuclear transporter
We further show that IPO13 interacts with and regulates the nuclear export of both Kruppel like factor 4 (KLF4) and Specificity Protein 1 (SP1) under conditions of oxidative stress, this transport function of IPO13 with respect to KLF4 and SP1 in response to oxidative stress likely contributing to modulation of cell survival under these conditions
To verify that IPO13 is a nuclear exporter of KLF4 and SP1 beyond the HeLa cell line, we examined the subcellular localisation of endogenous KLF4 and SP1 in response to H2O2 induced oxidative stress in the IPO13+/+ ESCs and how this compares in the IPO13−/− ESCs

Summary

Introduction

The importin superfamily member Importin-13 is a bidirectional nuclear transporter. To delineate its functional roles, we performed transcriptomic analysis on wild-type and Importin-13-knockout mouse embryonic stem cells, revealing enrichment of differentially expressed genes involved in stress responses and apoptosis regulation. 1 (SP1), a regulator of cell growth and development that can act as a cofactor in p53-mediated pro-apoptotic transcriptional repression[26,27], and Kruppel like factor 4 (KLF4)[28,29], a zinc finger containing transcription factor with roles in proliferation[30], differentiation[31], cell cycle arrest following DNA damage[32] and apoptosis In this context, we find that knock out of IPO13 protects mouse embryonic stem cells (mESCs) from oxidative stress-induced death, with siRNA knockdown of either SP1 or KLF4 in IPO13+/+ able to confer resistance to H2O2. To the best of our knowledge, our findings represent the first documented examples of IPOβ family-dependent nuclear transport of specific cargoes in stress, establishing a key role for IPO13 in stress responses through its ability to transport key factors in stress conditions

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