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Hepatocellular carcinoma (HCC) is the most common type of liver cancer in humans. The focal adhesion tyrosine kinase (FAK) is often over-expressed in human HCC and FAK inhibition may reduce HCC cell invasiveness. However, the anti-oncogenic effect of FAK knockdown in HCC cells remains to be clarified. We found that FAK depletion in HCC cells reduced in vitro and in vivo tumorigenicity, by inducing G2/M arrest and apoptosis, decreasing anchorage-independent growth, and modulating the expression of several cancer-related genes. Among these genes, we showed that FAK silencing decreased transcription and nuclear localization of enhancer of zeste homolog 2 (EZH2) and its tri-methylation activity on lysine 27 of histone H3 (H3K27me3). Accordingly, FAK, EZH2 and H3K27me3 were concomitantly upregulated in human HCCs compared to non-tumor livers. In vitro experiments demonstrated that FAK affected EZH2 expression and function by modulating, at least in part, p53 and E2F2/3 transcriptional activity. Moreover, FAK silencing downregulated both EZH2 binding and histone H3K27me3 levels at the promoter of its target gene NOTCH2. Finally, we found that pharmacological inhibition of FAK activity resembled these effects although milder. In summary, we demonstrate that FAK depletion reduces HCC cell growth by affecting cancer-promoting genes including the pro-oncogene EZH2. Furthermore, we unveil a novel unprecedented FAK/EZH2 crosstalk in HCC cells, thus identifying a targetable network paving the way for new anticancer therapies.

The activity of the nuclear factor-Y (NF-Y) transcription factor is restricted to proliferating cells in vitro. We engineered transgenic mice that enabled bioluminescence imaging of NF-Y activity in every area of the body. We visualized areas of proliferation, and we highlight for the first time a role of NF-Y activity in hepatocyte proliferation during liver regeneration.

In vivo imaging involving the use of genetically engineered animals is an innovative powerful tool for the noninvasive assessment of the molecular and cellular events that are often targets of therapy. On the basis of the knowledge that the activity of the nuclear factor-Y (NF-Y) transcription factor is restricted in vitro to proliferating cells, we have generated a transgenic reporter mouse, called MITO-Luc (for mitosis-luciferase), in which an NF-Y–dependent promoter controls luciferase expression. In these mice, bioluminescence imaging of NF-Y activity visualizes areas of physiological cell proliferation and regeneration during response to injury. Using this tool, we highlight for the first time a role of NF-Y activity on hepatocyte proliferation during liver regeneration. MITO-Luc reporter mice should facilitate investigations into the involvement of genes in cell proliferation and provide a useful model for studying aberrant proliferation in disease pathogenesis. They should be also useful in the development of new anti/proproliferative drugs and assessment of their efficacy and side effects on nontarget tissues.

NF-Y binds to CCAAT motifs in the promoter region of a variety of genes involved in cell cycle progression. The NF-Y complex comprises three subunits, NF-YA, -YB, and -YC, all required for DNA binding. Expression of NF-YA fluctuates during the cell cycle and is down-regulated in postmitotic cells, indicating its role as the regulatory subunit of the complex. Control of NF-YA accumulation is posttranscriptional, NF-YA mRNA being relatively constant. Here we show that the levels of NF-YA protein are regulated posttranslationally by ubiquitylation and acetylation. A NF-YA protein carrying four mutated lysines in the C-terminal domain is more stable than the wild-type form, indicating that these lysines are ubiquitylated Two of the lysines are acetylated in vitro by p300, suggesting a competition between ubiquitylation and acetylation of overlapping residues. Interestingly, overexpression of a degradation-resistant NF-YA protein leads to sustained expression of mitotic cyclin complexes and increased cell proliferation, indicating that a tight regulation of NF-YA levels contributes to regulate NF-Y activity.

NF-Y binds to CCAAT motifs in the promoter region of a variety of genes involved in cell cycle progression. The NF-Y complex comprises three subunits, NF-YA, -YB, and -YC, all required for DNA binding. Expression of NF-YA fluctuates during the cell cycle and is down-regulated in postmitotic cells, indicating its role as the regulatory subunit of the complex. Control of NF-YA accumulation is posttranscriptional, NF-YA mRNA being relatively constant. Here we show that the levels of NF-YA protein are regulated posttranslationally by ubiquitylation and acetylation. A NF-YA protein carrying four mutated lysines in the C-terminal domain is more stable than the wild-type form, indicating that these lysines are ubiquitylated Two of the lysines are acetylated in vitro by p300, suggesting a competition between ubiquitylation and acetylation of overlapping residues. Interestingly, overexpression of a degradation-resistant NF-YA protein leads to sustained expression of mitotic cyclin complexes and increased cell proliferation, indicating that a tight regulation of NF-YA levels contributes to regulate NF-Y activity.