USP7 and Daxx regulate mitosis progression and taxane sensitivity by affecting stability of Aurora-A kinase.

A large number of patients are resistant to taxane-based chemotherapy. Functional mitotic checkpoints are essential for taxane sensitivity. Thus, mitotic regulators are potential markers for therapy response and could be targeted for anticancer therapy. In this study, we identified a novel function of ubiquitin (Ub)-specific processing protease-7 (USP7) that interacts and cooperates with protein death domain-associated protein (Daxx) in the regulation of mitosis and taxane resistance. Depletion of USP7 impairs mitotic progression, stabilizes cyclin B and reduces stability of the mitotic E3 Ub ligase, checkpoint with forkhead and Ring-finger (CHFR). Consequently, cells with depleted USP7 accumulate Aurora-A kinase, a CHFR substrate, thus elevating multipolar mitoses. We further show that these effects are independent of the USP7 substrate p53. Thus, USP7 and Daxx are necessary to regulate proper execution of mitosis, partially via regulation of CHFR and Aurora-A kinase stability. Results from colony formation assay, in silico analysis across the NCI60 platform and in breast cancer patients suggest that USP7 levels inversely correlate with response to taxanes, pointing at the USP7 protein as a potential predictive factor for taxane response in cancer patients. In addition, we demonstrated that inhibition of Aurora-A attenuates USP7-mediated taxane resistance, suggesting that combinatorial drug regimens of Taxol and Aurora-A inhibitors may improve the outcome of chemotherapy response in cancer patients resistant to taxane treatment. Finally, our study offers novel insights on USP7 inhibition as cancer therapy.

Regulation of mitosis and taxane response by Daxx and Rassf1.

Current theories suggest that mitotic checkpoint proteins are essential for proper cellular response to taxanes, a widely used family of chemotherapeutic compounds. We recently showed that absence or depletion of protein Daxx increases cellular taxol (paclitaxel) resistance-a common trait of patients diagnosed with several malignancies, including breast cancer. Further investigation of Daxx-mediated taxol response revealed that Daxx is important for the proper timing of mitosis progression and cyclin B stability. Daxx interacts with mitotic checkpoint protein RAS-association domain family protein 1 (Rassf1) and partially colocalizes with this protein during mitosis. Rassf1/Daxx depletion or expression of Daxx-binding domain of Rassf1 elevates cyclin B stability and increases taxol resistance in cells and mouse xenograft models. In breast cancer patients, we observed the inverse correlation between Daxx and clinical response to taxane-based chemotherapy. These data suggest that Daxx and Rassf1 define a mitotic stress checkpoint that enables cells to exit mitosis as micronucleated cells (and eventually die) when encountered with specific mitotic stress stimuli, including taxol. Surprisingly, depletion of Daxx or Rassf1 does not change the activity of E3 ubiquitin ligase anaphase promotion complex/C in in vitro settings, suggesting the necessity of mitotic cellular environment for proper activation of this checkpoint. Daxx and Rassf1 may become useful predictive markers for the proper selection of patients for taxane chemotherapy.

Regulation of c-met expression by transcription repressor Daxx.

The protooncogene c-met encodes the tyrosine kinase receptor for the hepatocyte growth factor/scatter factor (HGF/SF). While overexpression of c-met is documented in many types of tumors, the mechanism of c-met regulation remains elusive. Here, we demonstrate Daxx as a repressor of c-met transcription. The expression of c-met is elevated in Daxx knockout mouse cells and is reversed by Daxx reconstitution. C-met promoter analysis of Daxx-/- cells reveled changes in chromatin acetylation, but not in DNA methylation. Daxx binds to the mouse c-met promoter and Daxx-binding region is sufficient for transcription repression, while HDAC2 is associated with c-met promoter mostly in Daxx+/+ cells, pointing to Daxx-dependent HDAC2 recruitment as a potential mechanism of c-met repression. HGF-induced cell mobility and invasion confirmed augmented activity of c-Met/HGF pathway in Daxx-/- cells. Finally, inverse correlation between Daxx and c-Met in cancer cell lines and in metastatic breast cancer specimens suggests potential function of Daxx as a c-met repressor during cancer progression.

[Usage of polymerase chain reaction in complex diagnosis of hepatitis B]. / Primenenie polimeraznoi tsepnoi reaktsii v kompleksnoi diagnostiki gepatita B.

Sera from 926 patients were analyzed by PCR using universal primers to surface gene of hepatitis B virus (HBV). HBV DNA was detected in 195 specimens. There were no serological markers of HBV in 8.2% of these sera, but later they were detected in patients' sera. In patients without HBV DNA in the serum, specific HBV antigens and antibodies were detected in 62%. Only in 14% of them the clinical picture of the disease corresponded to acute viral hepatitis, although the blood for PCR analysis was collected during the late stages of the infection. The rest cases were referred to mixed hepatitis C + D. Comparison of the results of PCR test and detection of serological virus replication markers HBeAg and HBeAb showed the presence of HBV DNA in 28% cases without HBeAg.

[The mental state of servicemen released from captivity]. / Psikhicheskoe sostoianie voennosluzhashchikh, osvobozhdennykh iz plena.

The clinical and medico-psychological research of the servicemen, long time staying by hostages in captivity is lead. Boundary mental frustration, in particular neurotic reactions and the conditions, asthenodepressive syndrome, posttraumatic stress frustrations, are revealed in 45.8% surveyed. The most psychotraumatic is initial period of adaptation to conditions of captivity. The necessity to carry out the measures of medico-psychological rehabilitation and treatment of the servicemen, released from captivity, should be taken into account during planning of medical maintenance of the troops in local wars and armed conflicts.

[Conservative motifs in enzyme superfamily catalyzing formation of acyladenylates and compounds with carboxy group]. / Konservativnye motivy v supersemeistve fermentov, kataliziruiushchikh obrazovanie atsiladenilatov iz ATP i soedinenii s karboksil'noi gruppoi.

The search of conserved motifs was performed in enzymes catalyzing acyladenylate formation using ATP as AMP-donor. Besides a known motif, we have found a second conserved motif. Screening the SWISS-PROT database for occurrence of the motifs have showed that both motifs are highly characteristic and occur in all proteins of this superfamily. The motifs are separated by 200-250 residues in all sequences. It may suggest that the both motifs belong to the structural unit involved in acyl adenylate formation.

[The efficacy of treating skin ulcers and burns with film dressings with antibiotics]. / Effektivnost' lecheniia iazv i ozhogov kozhi plenochnymi poviazkami s antibiotikami.

The article summarizes the results of studies conducted during the treatment of burns (108 patients), and ecthymas (85 patients) with the help of film dressing and antibiotic powder (R. Breitman's method). During application of this method the healing process was more rapid, the administration of antibiotics was minimum, the dressing process became more easy, good cosmetic results were obtained. The period of inpatient care was shortened, cost of treatment was reduced.

[The effect of substrates on stability of firefly luciferase, embedded in phosphatidylcholine liposomes]. / Vliianie substratov na stabil'nost' liutsiferazy svetliakov, vstroennoi v liposomy iz fosfatidilkholina.

The effects of substrates (ATP and luciferin) on stability of firefly luciferase embedded into phosphatidylcholine liposomes have been studied. Luciferin did not exert any appreciable influence on enzyme inactivation. Minor concentrations of adenosine 5'-triphosphate destabilized the enzyme; however, the increase in ATP concentration markedly stabilized the enzyme entrapped into liposomes. A kinetic scheme of ATP action on enzyme inactivation is proposed. According to this scheme, the enzyme has two ATP-binding sites.

[Immunomodulating peptides, regulation of interleukin-2 expression and its possible mechanism]. / Immunomoduliruiushchie peptidy, reguliatsiia obrazovaniia interleikina-2 i vozmozhnyi ee mekhanizm.

The influence of some immunomodulation peptides SKD, R and L on the interleukin-2 (IL-2) synthesis in T-lymphocytes and possibility of their specific interaction with nucleotide sequences of IL-2 gene were studied. It was firstly shown that peptides R and L specifically interacted with regulatory nucleotide sequences of IL-2 gene and, possibly, play a key role in the immunomodulation actions on the IL-2 production.