A new deletion of the mouse Y chromosome long arm associated with the loss of Ssty expression, abnormal sperm development and sterility

The mouse Y chromosome carries 10 distinct genes or gene families that have open reading frames suggestive of retained functionality; it has been assumed that many of these function in spermatogenesis. However, we have recently shown that only two Y genes, the testis determinant Sry and the translation initiation factor Eif2s3y, are essential for spermatogenesis to proceed to the round spermatid stage. Thus, any further substantive mouse Y-gene functions in spermatogenesis are likely to be during sperm differentiation. The complex Ssty gene family present on the mouse Y long arm (Yq) has been implicated in sperm development, with partial Yq deletions that reduce Ssty expression resulting in impaired fertilization efficiency. Here we report the identification of a more extensive Yq deletion that abolishes Ssty expression and results in severe sperm defects and sterility. This result establishes that genetic information (Ssty?) essential for normal sperm differentiation and function is present on mouse Yq.     

The catalytic domain of Escherichia coli Lon protease has a unique fold and a Ser-Lys dyad in the active site

ATP-dependent Lon protease degrades specific short-lived regulatory proteins as well as defective and abnormal proteins in the cell. The crystal structure of the proteolytic domain (P domain) of the Escherichia coli Lon has been solved by single-wavelength anomalous dispersion and refined at 1.75-A resolution. The P domain was obtained by chymotrypsin digestion of the full-length, proteolytically inactive Lon mutant (S679A) or by expression of a recombinant construct encoding only this domain. The P domain has a unique fold and assembles into hexameric rings that likely mimic the oligomerization state of the holoenzyme. The hexamer is dome-shaped, with the six N termini oriented toward the narrower ring surface, which is thus identified as the interface with the ATPase domain in full-length Lon. The catalytic sites lie in a shallow concavity on the wider distal surface of the hexameric ring and are connected to the proximal surface by a narrow axial channel with a diameter of approximately 18 A. Within the active site, the proximity of Lys(722) to the side chain of the mutated Ala(679) and the absence of other potential catalytic side chains establish that Lon employs a Ser(679)-Lys(722) dyad for catalysis. Alignment of the P domain catalytic pocket with those of several Ser-Lys dyad peptide hydrolases provides a model of substrate binding, suggesting that polypeptides are oriented in the Lon active site to allow nucleophilic attack by the serine hydroxyl on the si-face of the peptide bond.     

The spindle assembly checkpoint is not essential for CSF arrest of mouse oocytes

In Xenopus oocytes, the spindle assembly checkpoint (SAC) kinase Bub1 is required for cytostatic factor (CSF)-induced metaphase arrest in meiosis II. To investigate whether matured mouse oocytes are kept in metaphase by a SAC-mediated inhibition of the anaphase-promoting complex/cyclosome (APC/C) complex, we injected a dominant-negative Bub1 mutant (Bub1dn) into mouse oocytes undergoing meiosis in vitro. Passage through meiosis I was accelerated, but even though the SAC was disrupted, injected oocytes still arrested at metaphase II. Bub1dn-injected oocytes released from CSF and treated with nocodazole to disrupt the second meiotic spindle proceeded into interphase, whereas noninjected control oocytes remained arrested at metaphase. Similar results were obtained using dominant-negative forms of Mad2 and BubR1, as well as checkpoint resistant dominant APC/C activating forms of Cdc20. Thus, SAC proteins are required for checkpoint functions in meiosis I and II, but, in contrast to frog eggs, the SAC is not required for establishing or maintaining the CSF arrest in mouse oocytes.     

Synthetic peptides mimicking antigenic epitope of Helicobacter pylori urease

Short peptides resembling the Helicobacter pylori urease antigen (UreB F8 Ser-Ile-Lys-Glu-Asp-Val-Gln-Phe) with deleted aspartic acid and glutamic acid residues, anchored through a triazine linker via the N-terminal moiety to cellulose plate were prepared. The peptides were used for binding of antibodies from sera of patients with medically confirmed atherosclerosis. Recognition of the peptides was also tested with anti-Jack beans urease antibodies. The important role of a Gly-Gly spacer separating the peptides from the cellulose support was shown. Different patterns of binding of antibodies from H. pylori infected patients and anti-Jack bean urease antibodies were observed only in the case of pentapeptides. The peptide Gly-Gly-Leu-Val-Phe-Lys-Thr was recognized by most of the tested sera.     

Amino-terminal dimerization of peptides on the solid support. Synthesis and biological activity of the immunosuppressive HLA-DR fragments linked by poly(ethylene glycol)s

The nonapeptide fragment of the HLA-DR molecule, located in the exposed loop of the beta chain (164-172) and having the sequence VPRSGEVYT, suppresses the immune response. On the basis of the three-dimensional structure of the HLA-DR superdimer, we designed new dimeric analogs in which the VPRSGEVYT peptides are linked through their N-termini by poly(ethylene glycol) linkers of different lengths and are able to mimic the dimeric nature of the immunosuppressive fragments of HLA class II molecules. The analogs were synthesized using standard solid-phase peptide synthesis protocols. The dimerization was achieved by cross-linking the N-terminal positions of the peptides, attached to an MBHA resin, with alpha,omega-bis(acetic acid) poly(ethylene glycol), activated by esterification with pentafluorophenol. Our results demonstrate that the amino-terminal dimerization of the peptide results in enhanced immunosuppressive activity and that the potency of the conjugates depends on the length of the poly(ethylene glycol) linker. MS/MS analysis of the obtained dimeric peptides is also presented.     

Effects of hydroxyurea and aphidicolin on phosphorylation of ataxia telangiectasia mutated on Ser 1981 and histone H2AX on Ser 139 in relation to cell cycle phase and induction of apoptosis.

BACKGROUND: DNA replication stress often induces DNA damage. The antitumor drug hydroxyurea (HU), a potent inhibitor of ribonucleotide reductase that halts DNA replication through its effects on cellular deoxynucleotide pools, was shown to damage DNA inducing double-strand breaks (DSBs). Aphidicolin (APH), an inhibitor of alpha-like DNA polymerases, was also reported to cause DNA damage, but the evidence for induction of DSBs by APH is not straightforward. Histone H2AX is phosphorylated on Ser 139 in response to DSBs and one of the protein kinases that phosphorylate H2AX is ataxia telangiectasia mutated (ATM); activation of ATM is through its phosphorylation of Ser 1981. The present study was undertaken to reveal whether H2AX is phosphorylated in cells exposed to HU or APH and whether its phosphorylation is mediated by ATM. MATERIALS AND METHODS: HL-60 cells were treated in cultures with 0.1-5.0 mM HU or 1-4 muM APH for up to 5 h. Activation of ATM and H2AX phosphorylation was detected immunocytochemically using Ab specific to Ser1981-ATM or Ser 139-H2AX epitopes, respectively, concurrent with measurement of cellular DNA content. RESULTS: While exposure of cells to HU led to H2AX phosphorylation selectively during S phase and the cells progressing through the early portion of S (DI = 1.1-1.4) were more affected than late-S phase (DI = 1.6-1.9) cells, ATM was not activated by HU. In fact, the level of constitutive ("programmed") ATM phosphorylation was distinctly suppressed, in all phases of the cell cycle, at 0.1-5.0 mM HU. Cells' exposure to APH also resulted in H2AX phosphorylation at Ser139 with no evidence of ATM activation, and as in the case of HU, the early-S cells were more affected than the late-S phase cells. The rise in frequency of apoptotic cells became apparent after 2 h of exposure to HU or APH, and all apoptotic cells had markedly elevated levels of both H2AX-Ser139 and ATM-Ser1981 phosphorylation. CONCLUSIONS: The lack of correlation between H2AX phosphorylation and ATM activation indicates that protein kinase(s) other than ATM (ATR and/or DNA-dependent protein kinase) are activated by DSBs induced by replication stress. Interestingly, HU inhibits the constitutive ("programmed") level of ATM phosphorylation in untreated cells. However, DNA fragmentation during apoptosis activates ATM and dramatically increases level of H2AX phosphorylation.     

Optimization of 131I ablation in patients with differentiated thyroid carcinoma: comparison of early outcomes of treatment with 100 mCi versus 60 mCi

INTRODUCTION: The aim of this study was to compare the early outcomes between two groups of patients with differentiated thyroid carcinoma (DTC) who received 60 or 100 mCi of (131)I for remnant ablation. MATERIAL AND METHODS: 224 DTC patients with primary tumor > 1 cm of diameter or multifocal were randomised into prospective clinical trial. Patients with extrathyroideal extension of primary tumor and nodal metastases or M1 were not enrolled. 99 patients received 60 mCi, and 125--100 mCi of radioiodine as the first ablative dose. RESULTS: The effectiveness of thyroid ablation was evaluated after one year, during endogenous TSH (thyroid stimulating hormone) stimulation, and after two years during Lthyroxine therapy. Whole body scintigraphy (WBS) was performed under thyroxine withdrawal and thyroglobulin serum level was assessed. Distant micrometastases were detected in 9.8% of patients by post-therapy WBS, 11 patients in group A treated with 60 mCi and 11 in group B treated with 100 mCi. In other patients no symptoms of persistent disease were detected. At one year follow up full remission was diagnosed in 176 patients: 76 in group A and 100 in group B. The remaining ones, 13.3% and 11.2% respectively, received the second course of (131)I for remnant ablation. There were no statistically significant differences in Tg (thyroglobulin) serum level either 12 or 24 months after 131I treatment. CONCLUSIONS: Our evaluation of early efficacy of adjuvant radioiodine treatment in low risk DTC patients shows no differences between two radioiodine activities - 60 and 100 mCi in relation to thyroid ablation. Thus, the activity of 60 mCi is recommended.