Smyd3 is a transcriptional potentiator of multiple cancer-promoting genes and required for liver or colon cancer development

Smyd3 is a histone methyltransferase implicated in tumorigenesis. Here we show that Smyd3 expression in mice is required but not sufficient for chemically induced liver and colon cancer formation. In these organs Smyd3 is functioning in the nucleus as a direct transcriptional activator of several key genes involved in cell proliferation, epithelial-mesenchymal transition, JAK/Stat3 oncogenic pathways, as well as of the c-myc and b-catenin oncogenes. Smyd3 specifically interacts with H3K4Me3-modified histone tails and is recruited to the core promoter regions of many but not all active genes. Smyd3 binding density on target genes positively correlates with increased RNA Pol-II density and transcriptional outputs. The results suggest that Smyd3 is an essential transcriptional potentiator of a multitude of cancer-related genes. Overall design: Standard Smyd3-deficient (Smyd3-KO) mice were generated using gene-trap ES cell clones (AS0527 from International Gene Trap Consortium), in which a selection cassette, containing the splice acceptor site from mouse EN2 exon 2 followed by the beta-galactosidase and neomycin resistance gene fusion gene and the SV40 polyadenylation sequence was inserted into the 5th intron of the Smyd3 gene. The resulting mice were devoid of Smyd3 mRNA and protein in all tissues, including liver and colon. For the generation of Smyd3-Tg mice the open reading frame of the mouse Smyd3 cDNA, which contained 3 Flag epitopes at the 3’ end was inserted into the StuI site of the pTTR1-ExV3 plasmid (Yan et al, 1990). The 6.8 kb HindIII fragment containing the mouse transthyretin enhancer/promoter, intron 1, Smyd3 cDNA, three Flag epitopes and SV40 poly-A site was used to microinject C57Bl/6 fertilized oocytes. Founder animals were identified by Southern blotting and crossed with F1 mice to generate lines. Specific overexpression in the liver was tested by RT-PCR analysis in different tissues.

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Sarris ME, Moulos P, Haroniti A, Giakountis A, Talianidis I