Biotinyl-methyl 4-(amidomethyl)benzoate is a competitive inhibitor of human biotinidase

Colon cancer stemness as a reversible epigenetic state: Implications for anticancer therapies

The recent discovery of cancer cell plasticity, i.e. their ability to reprogram into cancer stem cells (CSCs) either naturally or under chemotherapy and/or radiotherapy, has changed, once again, the way we consider cancer treatment. If cancer stemness is a reversible epigenetic state rather than a genetic identity, opportunities will arise for therapeutic strategies that remodel epigenetic landscapes of CSCs. However, the systematic use of DNA methyltransferase and histone deacetylase inhibitors, alone or in combination, in advanced solid tumors including colorectal cancers, regardless of their molecular subtypes, does not seem to be the best strategy. In this review, we first summarize the knowledge researchers have gathered on the epigenetic signatures of CSCs with the difficulty of isolating rare populations of cells. We raise questions about the relevant use of currently available epigenetic inhibitors (epidrugs) while the expression of numerous cancer stem cell markers are often repressed by epigenetic mechanisms. These markers include the three cluster of differentiation CD133, CD44 and CD166 that have been extensively used for the isolation of colon CSCs.and . Finally, we describe current treatment strategies using epidrugs, and we hypothesize that, using correlation tools comparing associations of relevant CSC markers with chromatin modifier expression, we could identify better candidates for epienzyme targeting.

Triazole biotin: a tight-binding biotinidase-resistant conjugate

The natural amide bond found in all biotinylated proteins has been replaced with a triazole through CuAAC reaction of an alkynyl biotin derivative. The resultant triazole-linked adducts are shown to be highly resistant to the ubiquitous hydrolytic enzyme biotinidase and to bind avidin with dissociation constants in the low pM range. Application of this strategy to the production of a series of biotinidase-resistant biotin-Gd-DOTA contrast agents is demonstrated.

Identification of holocarboxylase synthetase chromatin binding sites in human mammary cell lines using the DNA adenine methyltransferase identification technology

Holocarboxylase synthetase (HCS) is a chromatin protein that is essential for mediating the covalent binding of biotin to histones. Biotinylation of histones plays crucial roles in the repression of genes and repeats in the human genome. We tested the feasibility of DNA adenine methyltransferase identification (DamID) technology to map HCS binding sites in human mammary cell lines. Full-length HCS was fused to DNA adenine methyltransferase (Dam) for subsequent transfection into breast cancer (MCF-7) and normal breast (MCF-10A) cells. HCS docking sites in chromatin were identified by using the unique adenine methylation sites established by Dam in the fusion construct; docking sites were unambiguously identified using methylation-sensitive digestion, cloning, and sequencing. In total, 15 novel HCS binding sites were identified in the two cell lines, and the following 4 of the 15 overlapped between MCF-7 and MCF-10A cells: inositol polyphosphate-5-phosphatase A, corticotropin hormone precursor, ribosome biogenesis regulatory protein, and leptin precursor. We conclude that DamID is a useful technology to map HCS binding sites in human chromatin and propose that the entire set of HCS binding sites could be mapped by combining DamID with microarray technology.

Cofactor chemogenomics

Cofactors are organic molecules, most of them originating from vitamins, that bind to enzymes making them able to catalyze defined reactions. A cofactor-based chemogenomics approach exploits the presence of a cofactor-binding domain to develop compound scaffolds tailored to mimic the cofactor and to replace it within target enzyme classes. As a result, a loss of function is observed. An expansion of the cofactor scaffold to include structural/chemical features derived from the substrate, that usually binds at cofactor adjacent sites, increases the specificity of the enzyme fishing. This approach has been so far applied only to NAD(P)(+)-dependent enzymes. However, it is suitable for all other cofactors, with difficulties, for some of them, originated by very tight binding. In the case of cofactors covalently bound to the enzyme, the competition between the natural cofactor and the cofactor scaffold mimic can only occur during enzyme folding.