Disruption of TFIIH activities generates a stress gene expression response and reveals possible new targets against cancer

Disruption of the enzymatic activities of the transcription factor TFIIH by the small molecules Triptolide (TPL) or THZ1 could be used against cancer. Here, we used the MCF10A-ErSrc oncogenesis model to compare the effect of TFIIH inhibitors between transformed cells and their progenitors. We report that tumour cells exhibited highly increased sensitivity to TPL or THZ1 and that the combination of both had a synergic effect. TPL affects the interaction between XPB and p52, causing a reduction in the levels of XPB, p52 and p8, but not other TFIIH subunits. RNA-Seq and RNAPII-ChIP-Seq experiments showed that although the levels of many transcripts were reduced, the levels of a significant number were increased after TPL treatment, with maintained or increased RNAPII promoter occupancy. A significant number of these genes encode for factors that have been related to tumour growth and metastasis, suggesting that transformed cells might rapidly develop resistance to TPL/THZ inhibitors. Some of these genes were also overexpressed in response to THZ1, of which depletion enhances the toxicity of TPL, and are possible new targets against cancer.

The DNA methylation drift of the atherosclerotic aorta increases with lesion progression

BACKGROUND

Atherosclerosis severity-independent alterations in DNA methylation, a reversible and highly regulated DNA modification, have been detected in aortic atheromas, thus supporting the hypothesis that epigenetic mechanisms participate in the pathogenesis of atherosclerosis. One yet unaddressed issue is whether the progression of atherosclerosis is associated with an increase in DNA methylation drift in the vascular tissue. The purpose of the study was to identify CpG methylation profiles that vary with the progression of atherosclerosis in the human aorta.

METHODS

We interrogated a set of donor-matched atherosclerotic and normal aortic samples ranging from histological grade III to VII, with a high-density (>450,000 CpG sites) DNA methylation microarray.

RESULTS

We detected a correlation between histological grade and intra-pair differential methylation for 1,985 autosomal CpGs, the vast majority of which drifted towards hypermethylation with lesion progression. The identified CpG loci map to genes that are regulated by known critical transcription factors involved in atherosclerosis and participate in inflammatory and immune responses. Functional relevance was corroborated by crossing the DNA methylation profiles with expression data obtained in the same human aorta sample set, by a transcriptome-wide analysis of murine atherosclerotic aortas and from available public databases.

CONCLUSIONS

Our work identifies for the first time atherosclerosis progression-specific DNA methylation profiles in the vascular tissue. These findings provide potential novel markers of lesion severity and targets to counteract the progression of the atheroma.

The Arabidopsis thaliana SET-domain-containing protein ASHH1/SDG26 interacts with itself and with distinct histone lysine methyltransferases

Polycomb group (PcG) and trithorax group (trxG) proteins are key regulators of homeotic genes and have central roles in cell proliferation, growth and development. In animals, PcG and trxG proteins form higher order protein complexes that contain SET domain proteins with histone methyltransferase activity, and are responsible for the different types of lysine methylation at the N-terminal tails of the core histone proteins. However, whether H3K4 methyltransferase complexes exist in Arabidopsis thaliana remains unknown. Here, we make use of the yeast two-hybrid system and the bimolecular fluorescence complementation assay to provide evidence for the self-association of the Arabidopsis thaliana SET-domain-containing protein SET DOMAIN GROUP 26 (SDG26), also known as ABSENT, SMALL, OR HOMEOTIC DISCS 1 HOMOLOG 1 (ASHH1). In addition, we show that the ASHH1 protein associates with SET-domain-containing sequences from two distinct histone lysine methyltransferases, the ARABIDOPSIS HOMOLOG OF TRITHORAX-1 (ATX1) and ASHH2 proteins. Furthermore, after screening a cDNA library we found that ASHH1 interacts with two proteins from the heat shock protein 40 kDa (Hsp40/DnaJ) superfamily, thus connecting the epigenetic network with a system sensing external cues. Our findings suggest that trxG complexes in Arabidopsis thaliana could involve different sets of histone lysine methyltransferases, and that these complexes may be engaged in multiple developmental processes in Arabidopsis.