The class II myosin MYH4 safeguards genome integrity and suppresses tumor progression
Jayashree Thatte, … , Maria Rossing, Claus S. Sørensen
Jayashree Thatte, … , Maria Rossing, Claus S. Sørensen
Published June 2, 2025
Citation Information: J Clin Invest. 2025;135(11):e188165. https://doi.org/10.1172/JCI188165.
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Research Article Cell biology Clinical Research Oncology

The class II myosin MYH4 safeguards genome integrity and suppresses tumor progression

Abstract

Loss-of-function mutations in genome maintenance genes fuel tumorigenesis through increased genomic instability. A subset of these tumor suppressors are challenging to identify due to context dependency, including functional interactions with other genes and pathways. Here, we searched for potential causal genes that impact tumor development and/or progression in breast cancer through functional-genetic screening of candidate genes. MYH4, encoding a class II myosin, emerged as a top hit impacting genomic stability. We show that MYH4 suppresses DNA replication stress by promoting replication licensing and replication fork progression. Moreover, we observed a strong synergistic relationship among class II myosins in suppressing replication-associated DNA damage. Genomic analysis of Pan-Cancer Analysis of Whole Genomes project breast cancer samples revealed frequent concomitant loss of TP53 with MYH4 and class II myosins on chromosome 17p. Notably, Myh4 disruption accelerated mouse mammary tumorigenesis in a Trp53-deficient background. In conclusion, our results suggest an unanticipated function of MYH4 in p53-mediated tumor suppression that can explain their combined loss in breast cancer.

Authors

Jayashree Thatte, Ana Moisés da Silva, Judit Börcsök, Thorkell Gudjónsson, Jan Benada, Xin Li, Muthiah Bose, Hanneke van der Gulden, Ji-Ying Song, Renée Menezes, Elena Martín-Doncel, Luis Toledo, Valdemaras Petrosius, Cord Brakebusch, Jos Jonkers, Finn Cilius Nielsen, Maria Rossing, Claus S. Sørensen

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Figure 3

MYH4 ensures replication licensing and promotes faithful replication.

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MYH4 ensures replication licensing and promotes faithful replication. (A...
(A) QIBC plot indicating EdU incorporation of U2OS cells transfected with indicated siRNAs for 48 hours. Boxes indicate cell cycle phases: blue, G1; green, S; and red, G2. Color threshold indicates mean γH2AX intensity in different cell cycle phases. Blue, minimum; red, maximum. (B) A pie chart indicating EdU- and DAPI-based cell cycle distribution of cells. (C) Statistics for mean EdU intensity in S phase. Data presented as mean ± SD. ***P < 0.001 by 2-tailed, paired t test. (D) QIBC plot of cells transfected with the indicated siRNAs and stained for chromatin-bound (CB) MCM2. Top panels: MCM2 distribution in cell cycle phases. Bottom panels: Mean intensity of CB MCM2. Color threshold: gray, minimum; blue, average; red, maximum. (E) A Western blot analysis of indicated proteins in soluble (SOL) and CB extracts from cells transfected with indicated siRNAs, n = 3. Note: Some of the blots were stripped and reblotted with different antibodies. (F) U2OS cells stably expressing DOX inducible, siRNA-resistant MYH4-GFP WT or ΔABD mutant, transfected with indicated siRNAs for 48 hours. The bar plots illustrate relative mean intensity of CB MCM2. Data presented as mean ± SD, n = 3. *P < 0.05, **P < 0.001 by 1-way ANOVA with Šidák’s multiple-comparison test. NS, not significant. (G) QIBC of cells transfected with the indicated siRNAs and stained for CB-PCNA. Top panel: PCNA distribution in cell cycle phases. Bottom panel: Mean intensity of γH2AX in the same set of cells, indicated with a box. (H) Representative confocal images showing PCNA and EdU staining after 48 hours of indicated siRNA transfection (n = 3). Scale bar: 20 μm. (I) Quantification of DNA fibers from cells transfected with indicated siRNAs and labeled with indicated analogs for indicated time. Error bars indicate ±SEM, n = 3. **P < 0.001 by 2-tailed, paired t test.