The ATRX–DAXX histone chaperone complex incorporates the histone variant H3.3 at heterochromatic regions in a replication-independent manner. Here, we present a high-resolution x-ray crystal structure of an interaction surface between ATRX and DAXX. We use single amino acid substitutions in DAXX that abrogate formation of the complex to explore ATRX-dependent and ATRX-independent functions of DAXX. We find that the repression of specific murine endogenous retroviruses is dependent on DAXX, but not on ATRX. In support, we reveal the existence of two biochemically distinct DAXX-containing complexes: the ATRX–DAXX complex involved in gene repression and telomere chromatin structure, and a DAXX–SETDB1–KAP1–HDAC1 complex that represses endogenous retroviruses independently of ATRX and H3.3 incorporation into chromatin. We find that histone H3.3 stabilizes DAXX protein levels and can affect DAXX-regulated gene expression without incorporation into nucleosomes. Our study demonstrates a nucleosome-independent function for the H3.3 histone variant.

Plasmids are and will remain important cloning vehicles for biotechnology. They have also been associated with the spread of a number of diseases and therefore are a subject of environmental concern. With the advent of sequencing technologies, the database of plasmids is increasing. It will be of immense importance to identify the various bacterial hosts in which the plasmid can replicate. The present review article describes the features that confer broad host range to the plasmids, the molecular basis of plasmid host range evolution, and applications in recombinant DNA technology and environment.

Purpose: Many transformed cells and embryonic stem cells are dependent on the biosynthesis of the universal methyl-donor S-adenosylmethionine (SAM) from methionine by the enzyme MAT2A to maintain their epigenome. We hypothesized that cancer stem cells (CSCs) rely on SAM biosynthesis and that the combination of methionine depletion and MAT2A inhibition would eradicate CSCs.Methods: Human triple (ER/PR/HER2)-negative breast carcinoma (TNBC) cell lines were cultured as CSC-enriched mammospheres in control or methionine-free media. MAT2A was inhibited with siRNAs or cycloleucine. The effects of methionine restriction and/or MAT2A inhibition on the formation of mammospheres, the expression of CSC markers (CD44 hi /C24 low ), MAT2A and CSC transcriptional regulators, apoptosis induction, and histone modifications were determined. A murine model of metastatic TNBC was utilized to evaluate the effects of dietary methionine restriction, MAT2A inhibition and the combination.Results: Methionine restriction inhibited mammosphere formation and reduced the CD44 hi / C24 low CSC population; these effects were partly rescued by SAM. Methionine depletion induced MAT2A expression (mRNA and protein) and sensitized CSCs to inhibition of MAT2A (siRNAs or cycloleucine). Cycloleucine enhanced the effects of methionine depletion on H3K4me3 demethylation and suppression of Sox9 expression. Dietary methionine restriction induced

Cisplatin has been considered as the crucial regimen of widely prescribed chemotherapy treatment for cancer. The advancing treatment of cancers has reached the border line, where tumors show resistance to cisplatin and may thwart its use. Other than issues of drug resistance, cisplatin has been reported to evince side effects such as nephrotoxicity and ototoxicity. Therefore, there is a compelling need to untangle the problems associated with cisplatin treatment in carcinoma. Areas covered: In this review, we summarize the current status of combinatorial options to bring about better pre-clinical and clinical cisplatin drug responses in carcinoma. We begin with problems associated with cisplatin drugs and current avenues such as depicting molecular modulation of enhanced influx and reduced efflux. We also discuss the scope of the DNA damage response landscape and contribution of regulatory small RNAs towards potentiation of cisplatin responses. Expert commentary: The extensive use of cisplatin and incessant high drug dose have prompted the scientific community to limit the burden of cisplatin without compromising therapeutic success. Currently, there are reports on the potential use of other non-toxic small molecule inhibitors, interference RNAs and peptide mimetics to get rid of cellular adversities responsible for cisplatin resistance and high dose effects.