Woohwangcheongsimwon Prevents High-Fat Diet-Induced Memory Deficits and Induces SIRT1 in Mice.

Woohwangcheongsimwon (WHC) is a mixture of herbal medicines that is widely prescribed in Korean traditional medicine. SIRT1 is known for its regulatory roles in energy metabolism, oxidative stress, and circadian rhythms. This study was designed to determine whether WHC can increase and mimic the biological reactions of SIRT1 activation. Ten-month-old male mice were divided into four groups: nontreated normal diet (ND), nontreated high-fat diet (HFD), WHC-treated ND, and WHC-treated HFD. Body weight and cognitive functions were evaluated after treatment. The hippocampal expressions of SIRT1 and PGC-1α were also measured. The components of WHC were identified by liquid chromatography. High-fat diet-fed mice gained more weight and demonstrated greater deficits in short-term and long-term cognitive functions. WHC suppressed the deleterious effects of a HFD on weight gain and cognitive decline, but showed no prominent effects on animals fed NDs. The herbal treatment also increased the expression of SIRT1 and PGC-1α in the hippocampus. Despite the induction of hippocampal SIRT1 expression by WHC, resveratrol was not present among the natural compounds identified. This expression might have contributed to the suppression of high-fat diet-induced memory deficits in mice treated with the herbal mixture.

Identification of novel substrates for human checkpoint kinase Chk1 and Chk2 through genome-wide screening using a consensus Chk phosphorylation motif.

Checkpoint kinase 1 (Chk1) and Chk2 are effector kinases in the cellular DNA damage response and impairment of their function is closely related to tumorigenesis. Previous studies revealed several substrate proteins of Chk1 and Chk2, but identification of additional targets is still important in order to understand their tumor suppressor functions. In this study, we screened novel substrates for Chk1 and Chk2 using substrate target motifs determined previously by an oriented peptide library approach. The potential candidates were selected by genome-wide peptide database searches and were examined by in vitro kinase assays. ST5, HDAC5, PGC-1alpha, PP2A PR130, FANCG, GATA3, cyclin G, Rad51D and MAD1a were newly identified as in vitro substrates for Chk1 and/or Chk2. Among these, HDAC5 and PGC-1a were further analyzed to substantiate the screening results. Immunoprecipitation kinase assay of full-length proteins and site-directed mutagenesis analysis of the target motifs demonstrated that HDAC5 and PGC-1alpha were specific targets for Chk1 and/or Chk2 at least in vitro.

Nek6 is involved in G2/M phase cell cycle arrest through DNA damage-induced phosphorylation.

Nek6 is a recently identified NIMA-related kinase that is required for mitotic cell cycle progression. In the present study, we examined the role of Nek6 in the DNA damage response. We found that Nek6 is phosphorylated upon IR and UV irradiation through the DNA damage checkpoint in vivo. Nek6 is also directly phosphorylated by the checkpoint kinases Chk1 and Chk2 in vitro. Notably, Nek6 activation during mitosis is completely abolished by IR and UV irradiation. Moreover, the ectopic expression of Nek6 overrides DNA damage-induced G(2)/M arrest. These results suggest that Nek6 is a novel target of the DNA damage checkpoint and that the inhibition of Nek6 activity is required for proper cell cycle arrest in the G(2)/M phase upon DNA damage.

Alkylating agent methyl methanesulfonate (MMS) induces a wave of global protein hyperacetylation: implications in cancer cell death.

Protein acetylation modification has been implicated in many cellular processes but the direct evidence for the involvement of protein acetylation in signal transduction is very limited. In the present study, we found that an alkylating agent methyl methanesulfonate (MMS) induces a robust and reversible hyperacetylation of both cytoplasmic and nuclear proteins during the early phase of the cellular response to MMS. Notably, the acetylation level upon MMS treatment was strongly correlated with the susceptibility of cancer cells, and the enhancement of MMS-induced acetylation by histone deacetylase (HDAC) inhibitors was shown to increase the cellular susceptibility. These results suggest protein acetylation is important for the cell death signal transduction pathway and indicate that the use of HDAC inhibitors for the treatment of cancer is relevant.