Design,synthesis and biological evaluation of novel 3-substituted pyrazolopyrimidine derivatives as potent Bruton’s tyrosine kinase (BTK) inhibitors

A series of 3-substituted pyrazolopyrimidine derivatives as BTK inhibitors were designed by structure-based drug design and they were synthesized, evaluated by enzyme-based assay and anti-proliferation against Ramos and Raji cells. Most of them displayed good inhibitory activities against both BTK and B-cell lymphoblastic leukemia lines in vitro. Among them, compound 8a exhibited excellent potency (IC₅₀?=?7.95?nM against BTK enzyme, 8.91?μM against Ramos cells and 1.80?μM against Raji cells), with a better hydrophilicity (ClogP?=?3.33). These explorations provided new clues to discover 3-substituted pyrazolopyrimidine derivatives as novel anti-tumor agents.     

SP1 acts as a key factor, contributes to upregulation of ADAM23 expression under serum deprivation

ADAM23 modulates many cellular functions, alteration of expression causes a number of tumor types; however, the mechanisms controlling ADAM23 expression remain unknown. Here we have identified a SP1 binding site (−202/−190) that binds SP1 at the proximal promoter of human ADAM23 gene; furthermore, serum deprivation enhances open chromatin accessibility and help expose the SP1 binding site; finally, SP1 binding recruits RNA polymerase II, which in turn results in upregulation of endogenous ADAM23 expression. Therefore, the present study delineates the fundamental elements of a core promoter structure that will be helpful for future studies of the regulation of ADAM23 gene.     

Novel nucleosomal particles containing core histones and linker DNA but no histone H1

Eukaryotic chromosomal DNA is assembled into regularly spaced nucleosomes, which play a central role in gene regulation by determining accessibility of control regions. The nucleosome contains ∼147 bp of DNA wrapped ∼1.7 times around a central core histone octamer. The linker histone, H1, binds both to the nucleosome, sealing the DNA coils, and to the linker DNA between nucleosomes, directing chromatin folding. Micrococcal nuclease (MNase) digests the linker to yield the chromatosome, containing H1 and ∼160 bp, and then converts it to a core particle, containing ∼147 bp and no H1. Sequencing of nucleosomal DNA obtained after MNase digestion (MNase-seq) generates genome-wide nucleosome maps that are important for understanding gene regulation. We present an improved MNase-seq method involving simultaneous digestion with exonuclease III, which removes linker DNA. Remarkably, we discovered two novel intermediate particles containing 154 or 161 bp, corresponding to 7 bp protruding from one or both sides of the nucleosome core. These particles are detected in yeast lacking H1 and in H1-depleted mouse chromatin. They can be reconstituted in vitro using purified core histones and DNA. We propose that these ‘proto-chromatosomes’ are fundamental chromatin subunits, which include the H1 binding site and influence nucleosome spacing independently of H1.     

Sex-specific alterations in chromatin conformation of the brain of aging mouse

Chromatin conformation has been analysed in the brain cortex of adult (24±2 weeks) and old (65±4 weeks) male and female mice. Nuclei purified from different groups of mice were digested with MNase and DNase I for varying time periods (0–90 min), and with endogenous endonucleases for 1 h. MNase and DNase I digestion kinetics showed that the percentage of acid solubility of chromatin was relatively lower in old than adult and in female than male. This was further supported by electrophoretic analysis of nuclease digested DNA fragments. When the nuclei were incubated with only Ca²⁺or mg²⁺, no endonuclease digestion was observed. However, under similar conditions, the liver DNA was cleaved substantially. When divalent cations were added together, they activated endogenous endonucleases and digested the brain chromatin. The activity of Ca²⁺/Mg²⁺-dependent endogenous endonucleases was higher in male than female. Thus the accessibility of chromatin to MNase, DNase I and endogenous endonucleases was higher in male than female, and MNase as well as DNase I were more active in adult than old. Such sex- and age-dependent conformation of chromatin may attribute to differential expression of genes in the mouse brain.     

Mammalian ChlR1 has a role in heterochromatin organization

The ChlR1 DNA helicase, encoded by DDX11 gene, which is responsible for Warsaw breakage syndrome (WABS), has a role in sister-chromatid cohesion. In this study, we show that human ChlR1 deficient cells exhibit abnormal heterochromatin organization. While constitutive heterochromatin is discretely localized at perinuclear and perinucleolar regions in control HeLa cells, ChlR1-depleted cells showed dispersed localization of constitutive heterochromatin accompanied by disrupted centromere clustering. Cells isolated from Ddx11^−/− embryos also exhibited diffuse localization of centromeres and heterochromatin foci. Similar abnormalities were found in HeLa cells depleted of combinations of HP1α and HP1β. Immunofluorescence and chromatin immunoprecipitation showed a decreased level of HP1α at pericentric regions in ChlR1-depleted cells. Trimethyl-histone H3 at lysine 9 (H3K9-me3) was also modestly decreased at pericentric sequences. The abnormality in pericentric heterochromatin was further supported by decreased DNA methylation within major satellite repeats of Ddx11^−/− embryos. Furthermore, micrococcal nuclease (MNase) assay revealed a decreased chromatin density at the telomeres. These data suggest that in addition to a role in sister-chromatid cohesion, ChlR1 is also involved in the proper formation of heterochromatin, which in turn contributes to global nuclear organization and pleiotropic effects.