Identification and mechanistic characterization of low-molecular-weight inhibitors for HuR


Careful regulation of mRNA half-lives is a fundamental mechanism allowing cells to quickly respond to changing environmental conditions. The mRNA-binding Hu proteins are important for stabilization of short-lived mRNAs. Here we describe the identification and mechanistic characterization of the first low-molecular-weight inhibitors for Hu protein R (HuR) from microbial broths (Actinomyces sp.): dehydromutactin (1), MS-444 (2) and okicenone (3). These compounds interfere with HuR RNA binding, HuR trafficking, cytokine expression and T-cell activation. A mathematical and experimental analysis of the compounds' mode of action suggests that HuR homodimerizes before RNA binding and that the compounds interfere with the formation of HuR dimers. Our results demonstrate the chemical drugability of HuR; to our knowledge HuR is the first example of a drugable protein within the Hu family. MS-444, dehydromutactin and okicenone may become valuable tools for studying HuR function. An assessment of HuR inhibition as a central node in malignant processes might open up new conceptual routes toward combatting cancer.

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Figure 1: Identification of HuR inhibitors by confocal high-throughput screening.
Figure 2: HuR ARE binding inhibition by 1 and 2.
Figure 3: Inhibition of HuR homodimerization by 1, 2 and 3.
Figure 4: Experimental evidence for inhibition of HuR homodimerization by 1 and 2.
Figure 5: Direct binding of 3 to HuR, monitored by microdialysis.
Figure 6: Effect of 1 and 2 on primary human T cells.
Figure 7: 2 decreases ARE cytokine expression in activated primary human monocytes.

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The authors thank R. Amstutz and J.E. DeVries for continuous support, and P. Fürst for reviewing the manuscript. This work was supported by a scholarship from the Austrian Academy of Sciences.

Author information




N.-C.M. and V.U. established the screening assay. J.O. performed the high-throughput screen. L.O., C.G., S.M. and H.-U.N. isolated the compounds and elucidated the structures. N.-C.M. and M.H. performed the compound selection and mechanistic compound characterization. M.H. assessed structure-related literature information. J.-M.S. was responsible for the analytics and reagent preparation. N.-C.M. and J.-M.S. performed the microdialysis experiments. C.B. was responsible for the instrumental setup for confocal imaging experiments, which were performed by N.-C.M. and R.B. N.H. performed the cytokine expression experiments. The project was designed and coordinated by N.-C.M. and M.A. N.-C.M., M.H. and M.A. wrote the manuscript. All authors discussed the results and commented on the manuscript.

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Correspondence to Nicole-Claudia Meisner or Martin Hintersteiner.

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Competing interests

All authors are employed by Novartis Institutes for Biomedical Research. K.M. was employed by Novartis but is now retired.

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Supplementary Figures 1–6, Supplementary Table 1 and Supplementary Methods (PDF 2782 kb)

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Meisner, NC., Hintersteiner, M., Mueller, K. et al. Identification and mechanistic characterization of low-molecular-weight inhibitors for HuR. Nat Chem Biol 3, 508–515 (2007).

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