Isoginkgetin increases the expression of metal responsive transcripts but inhibits their translation

Abstract

Isoginkgetin (IGG) is a natural bioflavonoid isolated initially from leaf extracts of Gingko biloba trees used in traditional Chinese medicine. We previously reported that IGG strongly inhibits nascent protein synthesis by activating the shared ATF4-dependent branches of the integrated stress response (ISR) and the unfolded protein response (UPR). 

Introduction

Isoginkgetin (IGG) is a natural bioflavonoid derived from Ginkgo biloba trees and abundant in Ginkgo biloba extracts [1]. These extracts have long been used in traditional Chinese medicine for their anti-inflammatory properties [1,2]. In 2008, IGG was identified in a chemical screen as a potent small molecule inhibitor of the spliceosome [2]. 

Materials and method

Cell culture and drug treatment

HCT116, HeLa and U-2 OS cells were obtained from the American Tissue Type Collection (Cat #: CCL-247, CCL-2, and HTB-96, Manassas, VA). An HCT116-derived subline (HCT116 ATF4-def) that does not express ATF4 was previously generated in our lab using a tandem guide CRISPR-Cas9 strategy [8]. Normal human neonatal foreskin fibroblasts expressing human telomerase reverse transcriptase (NFhTERT) were obtained from Mats Ljungman (University of Michigan) [11]. 

Results

IGG induces metal responsive transcripts in an ATF4-independent manner

We have previously reported that IGG increased the expression of 4 metallothionines and a metal responsive zinc transporter in HCT116 colon cancer cells [6,8]. While the predominant transcriptional response involved the ATF4 transcription factor, this metal response appeared to be ATF4-independent in our RNA sequencing (RNA-seq) data set [6]. 

Discussion

IGG was first reported in the literature in the early 1980’s as one of several biflavones isolated from G. biloba leaf extracts [20]. It was later found to inhibit cell growth in culture and induce apoptosis in a variety of cell lines [21–23]. The precise target of IGG contributing to these biological effects has yet to be determined but, IGG was identified in a chemical screen as a potent small molecule inhibitor of the spliceosome [24].

Conclusion

Existing research on cellular responses to IGG have revealed the broad cellular activity and potential anti-neoplastic effects of IGG, though detailed mechanistic responses to IGG and direct consequences of its splicing inhibitory activity are not fully defined. Here, we further established that IGG induces the expression of a group of MTs and ZnT1 involved in the RMI at the mRNA but not protein level, independent of ATF4.

Citation: Peneycad C, van Zyl E, Mohur A, McKay BC (2026) Isoginkgetin increases the expression of metal responsive transcripts but inhibits their translation. PLoS One 21(6): e0352014. https://doi.org/10.1371/journal.pone.0352014

Editor: Patrick Goymer, Public Library of Science, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND

Received: August 14, 2025; Accepted: June 4, 2026; Published: June 25, 2026

Copyright: © 2026 Peneycad et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the manuscript and its Supporting Information files. Supporting information includes uncropped immunoblots and all data presented in graphs in Figs 1, 2, 3, 4, 6, 7, 8 and 9.

Funding: Natural Sciences and Engineering Research Council of Canada RGPIN- 2019-06146 and RGPIN-2025-04489 to B.C.M. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.