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Human myeloid leukemia cells (HL-60/S4) exposed to hyperosmotic stress with sucrose undergo dehydration and cell shrinkage. Interphase chromatin and mitotic chromosomes congeal, exhibiting altered phase separation (demixing) of chromatin proteins. To investigate changes in the transcriptome, we exposed HL-60/S4 cells to hyperosmotic sucrose stress (~600 milliOsmolar) for 30 and 60 minutes. We employed RNA-Seq of polyA mRNA to identify genes with increased or decreased transcript levels relative to untreated control cells (i.e., differential gene expression). These genes were examined for over-representation of Gene Ontology (GO) terms. In stressed cells, multiple GO terms associated with transcription, translation, mitochondrial function and proteosome activity, as well as "replication-dependent histones", were over-represented among genes with increased transcript levels; whereas, genes with decreased transcript levels were over-represented with transcription repressors. The transcriptome profiles of hyperosmotically-stressed cells suggest acquisition of cellular rebuilding, a futile homeostatic response, as these cells are ultimately doomed to a dehydrated death. [ABSTRACT FROM AUTHOR]

This article, titled "50th Anniversary of the Nucleosome Discovery: a Brief Essay," discusses the groundbreaking discovery of nucleosomes in 1974. Prior to this discovery, it was believed that histone proteins covered DNA, creating irregular fibers. However, electron micrographs revealed that nucleosome beads represent a defined structure with histones on the inside and DNA coiled around the outside. This discovery simplified our understanding of chromatin structure, but subsequent research has shown the complexity of histone variants and epigenetic modifications. Current chromatin research focuses on higher levels of structure and regulation. [Extracted from the article]