We identify the SUMO-Targeted Ubiquitin Ligase (STUbL) family of proteins and propose that STUbLs selectively ubiquitinate sumoylated proteins and proteins that contain SUMO-like domains (SLDs). STUbL recruitment to sumoylated/SLD proteins is mediated by tandem SUMO interaction motifs (SIMs) within the STUbLs N-terminus. STUbL-mediated ubiquitination maintains sumoylation pathway homeostasis by promoting target protein desumoylation and/or degradation. Thus, STUbLs establish a novel mode of communication between the sumoylation and ubiquitination pathways. STUbLs are evolutionarily conserved and include: Schizosaccharomyces pombe Slx8-Rfp (founding member), Homo sapiens RNF4, Dictyostelium discoideum MIP1 and Saccharomyces cerevisiae Slx5-Slx8. Cells lacking Slx8-Rfp accumulate sumoylated proteins, display genomic instability, and are hypersensitive to genotoxic stress. These phenotypes are suppressed by deletion of the major SUMO ligase Pli1, demonstrating the specificity of STUbLs as regulators of sumoylated proteins. Notably, human RNF4 expression restores SUMO pathway homeostasis in fission yeast lacking Slx8-Rfp, underscoring the evolutionary functional conservation of STUbLs. The DNA repair factor Rad60 and its human homolog NIP45, which contain SLDs, are candidate STUbL targets. Consistently, Rad60 and Slx8-Rfp mutants have similar DNA repair defects.

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Spy1 is the originally identified member of the Speedy/Ringo family of vertebrate cell cycle regulators, which can control cell proliferation and survival through the atypical activation of cyclin-dependent kinases. Here we report a role for Spy1 in apoptosis and checkpoint activation in response to UV irradiation. Using an inducible system allowing for regulated expression of Spy1, we show that Spy1 expression prevents activation of caspase-3 and suppresses apoptosis in response to UV irradiation. Spy1 expression also allows for UV irradiation-resistant DNA synthesis and permits cells to progress into mitosis, as demonstrated by phosphorylation on histone H3, indicating that Spy1 expression can inhibit the S-phase/replication and G 2 /M checkpoints. We demonstrate that Spy1 expression inhibits phosphorylation of Chk1, RPA, and histone H2A.X, which may directly contribute to the decrease in apoptosis and checkpoint bypass. Furthermore, mutation of the conserved Speedy/ Ringo box, known to mediate interaction with CDK2, abrogates the ability of Spy1 to inhibit apoptosis and the phosphorylation of Chk1 and RPA. The data presented indicate that Spy1 expression allows cells to evade checkpoints and apoptosis and suggest that Spy1 regulation of CDK2 is important for the response to DNA damage.

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The human core promoter binding protein (hCPBP) has been identified as a DNA-binding protein involved in the regulation of TATA box-less genes like those encoding the pregnancy-specific glycoproteins. Structurally, hCPBP contains three zinc fingers in the C-terminal domain, which is highly conserved in a number of proteins that constitute the Krüppel-like family of transcription factors. In the present work, we report the molecular cloning of the mouse CPBP (mCPBP) and its expression pattern during development as well as in adult tissues. The mouse cDNA encodes a protein of 283 amino acids that share 94.4% of identity with the hCPBP. The highest level of mCPBP transcript was detected in placenta, and its expression was lower in total embryos and in adult tissues. We also show by in situ hybridization that during embryonic development the mCPBP gene is mainly expressed in extra-embryonic structures throughout gestation; essentially no specific expression was detected in embryonic tissues. Our data demonstrate that CPBP transcript is enriched in the trophoblastic tissue and strongly suggest that its encoded polypeptide regulates target genes involved in placental development and pregnancy maintenance.

Aim. To study the presence and localization of the P2X and P2Y receptor subtypes in the human cystic artery and great saphenous vein (with and without varicose disease).Methods. Segments of the human blood vessels were stained using a standard two-step immunohistochemical analysis using primary and secondary antibodies. In the experiments primary antibodies to the following receptors were used: Р2Х1, Р2Х2, Р2Х3, Р2Х4, Р2Y1, Р2Y2, Р2Y4. In order to determine the presence of a receptor in a vessel sample a comparison was made between staining of the experimental and the control samples, which were not treated with primary antibodies.Results. Immunohistochemical analysis of the cystic artery showed the presence of Р2Х1, Р2Х3, Р2Y1, Р2Y2 receptors. All receptor subtypes were found to be located in the muscular layer of the artery, whereas the P2Y1 receptor was also expressed on the surface of the endothelial cells. In the great saphenous vein without varicose disease Р2Х1, Р2Х2 и Р2Y1 receptor subtypes were identified, all of which were found to be located on the smooth muscle cells of the vein. Similarly to the cystic artery, the Р2Y1 receptor was also found within the endothelial layer of the vein. At the same time, only Р2Х2 и Р2Y1 receptor subtypes were expressed in the muscular layer of the great saphenous vein affected by varicose disease. No P2 receptor subtypes were identified on the endothelial layer of the varicose-diseased vein.Conclusion. Different P2 receptor subtypes were found to be present in the smooth muscle and endothelial layers of the human cystic artery and great saphenous vein. The identified differences in the receptor subtypes between samples of great saphenous veins with and without varicose disease are, most likely, explained by the restructuring of the receptor apparatus as a result of varicose disease progression.

Results of the study suggest that the sutureless sublay technique is safe and effective in the treatment of ventral abdominal hernia, especially in small and medium defects.

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