High level of divergence of male-reproductive-tract proteins, between Drosophila melanogaster and its sibling species, D. simulans

We compared male-reproductive-tract polypeptides of Drosophila melanogaster and D. simulans by using two-dimensional gel electrophoresis. Approximately 64% of male-reproductive-tract polypeptides were identical between two randomly chosen isofemale lines from these two species, compared with 83% identity for third-instar imaginal wing-disc polypeptides. Qualitatively similar differences were found between reproductive tracts and imaginal discs when D. sechellia was compared with D. melanogaster and with D. simulans. When genic polymorphism was taken into account, approximately 10% of male- reproductive-tract polypeptides were apparently fixed for different alleles between D. melanogaster and D. simulans; this proportion is the same as that found for soluble enzymes by one-dimensional gel electrophoresis. Strikingly, approximately 20% of male-reproductive- tract polypeptides of either D. melanogaster or D. simulans had no detectable homologue in the other species. We propose that proteins of the Drosophila male reproductive tract may have diverged more extensively between species than have other types of proteins and that much of this divergence may involve large changes in levels of polypeptide expression.      

Pre-induction priming of the uterine cervix with oral prostaglandin E2 and a placebo

A double blind study was undertaken to determine the effectiveness or oral prostaglandin E2 as a means of improving the pelvic score prior to induction of labour. 48 patients who were greater than 37 were gestation and who had Bishop scores of less than 6 entered the study. Ten tablets were given on an hourly regime. Of 25 patients in the prostaglandin group, 17 were considered successes (68.0%), whereas of 23 patients who received a placebo, 9 were successes (39.1%). No adverse effects were recorded. Prostaglandin E2 is therefore considered a safe and effective method for priming the unfavourable cervix prior to induction of labour.     

Monoclonal antibodies to rabbit liver cytochrome P-448

Cytochrome P-448 (mol wt 55,000 Daltons) from rabbit liver was purified to a specific content of 16.6 nmol/mg. Mice were immunised with this preparation, their spleens removed and dissociated lymphocytes hybridised with myeloma cells. Four monoclonal antibodies against cytochrome P-448 were raised and partially characterised. All four antibodies interacted with cytochrome P-448 in intact microsomal fractions and selectively immunoadsorbed cytochrome P-448 from solubilised microsomal preparations. One of the antibodies inhibited benzo[a] pyrene hydroxylase activity in a reconstituted system, one had no effect on activity and two increased activity. The possible applications of such antibodies are discussed.     

Atm deficiency affects both apoptosis and proliferation to augment Myc-induced lymphomagenesis

Myc oncoproteins are commonly activated in malignancies and are sufficient to provoke many types of cancer. However, the critical mechanisms by which Myc contributes to malignant transformation are not clear. DNA damage seems to be an important initiating event in tumorigenesis. Here, we show that although Myc does not directly induce double-stranded DNA breaks, it does augment activation of the Atm/p53 DNA damage response pathway, suggesting that Atm may function as a guardian against Myc-induced transformation. Indeed, we show that Atm loss augments Myc-induced lymphomagenesis and impairs Myc-induced apoptosis, which normally harnesses Myc-driven tumorigenesis. Surprisingly, Atm loss also augments the proliferative response induced by Myc, and this augmentation is associated with enhanced suppression of the expression of the cyclin-dependent kinase inhibitor p27(Kip1). Therefore, regulation of cell proliferation and p27(Kip1) seems to be a contributing mechanism by which Atm holds tumor formation in check.     

BRCA1 is required for common-fragile-site stability via its G2/M checkpoint function

Common fragile sites are loci that form chromosome gaps or breaks when DNA synthesis is partially inhibited. Fragile sites are prone to deletions, translocations, and other rearrangements that can cause the inactivation of associated tumor suppressor genes in cancer cells. It was previously shown that ATR is critical to fragile-site stability and that ATR-deficient cells have greatly elevated fragile-site expression (A. M. Casper, P. Nghiem, M. F. Arlt, and T. W. Glover, Cell 111:779-789, 2002). Here we demonstrate that mouse and human cells deficient for BRCA1, due to mutation or knockdown by RNA interference, also have elevated fragile-site expression. We further show that BRCA1 functions in the induction of the G(2)/M checkpoint after aphidicolin-induced replication stalling and that this checkpoint function is involved in fragile-site stability. These data indicate that BRCA1 is important in fragile-site stability and that fragile sites are recognized by the G(2)/M checkpoint pathway, in which BRCA1 plays a key role. Furthermore, they suggest that mutations in BRCA1 or interacting proteins could lead to rearrangements at fragile sites in cancer cells.     

Growth of <Emphasis Type="Italic">Helicobacter pylori</Emphasis> in a long spiral form does not alter expression of immunodominant proteins

Background  

We have previously reported that altered culture conditions (a broth media with shaking) could induce a strain of Helicobacter pylori to assume a long spiral morphology resembling that described for Helicobacter heilmannii. The present study was initiated to determine if other strains of H. pylori could be induced to assume that morphology and if doing so would alter the expression of immunodominant proteins.     

The many substrates and functions of ATM

As its name suggests, the ATM--'ataxia-telangiectasia, mutated'--gene is responsible for the rare disorder ataxia-telangiectasia. Patients show various abnormalities, mainly in their responses to DNA damage, but also in other cellular processes. Although it is hard to understand how a single gene product is involved in so many physiological processes, a clear picture is starting to emerge.     

Wild-type p53: tumors can't stand it

Most malignant tumors disrupt the p53 signaling pathway in order to grow and survive. Although many genes in addition to p53 are mutated in tumors, recent studies by Ventura et al. (2007) and Xue et al. (2007) suggest that restoring p53 function alone is sufficient to cause regression of several different tumor types in mice and thus might represent a potent therapeutic strategy to treat certain human cancers. Martins et al. (2006) also demonstrate that restoration of p53 activity results in tumor regression but add the sobering caveat that tumors may be able to quickly generate resistance by finding other ways to disrupt the p53 pathway.     

Roles of ATM and NBS1 in chromatin structure modulation and DNA double-strand break repair

We developed a novel system to create DNA double-strand breaks (DSBs) at defined endogenous sites in the human genome, and used this system to detect protein recruitment and loss at and around these breaks by chromatin immunoprecipitation (ChIP). The detection of human ATM protein at site-specific DSBs required functional NBS1 protein, ATM kinase activity and ATM autophosphorylation on Ser 1981. DSB formation led to the localized disruption of nucleosomes, a process that depended on both functional NBS1 and ATM. These two proteins were also required for efficient recruitment of the repair cofactor XRCC4 to DSBs, and for efficient DSB repair. These results demonstrate the functional importance of ATM kinase activity and phosphorylation in the response to DSBs, and support a model in which ordered chromatin structure changes that occur after DNA breakage depend on functional NBS1 and ATM, and facilitate DNA DSB repair.