SUMO modification of PCNA is controlled by DNA

Post-translational modification by the ubiquitin-like protein SUMO is often regulated by cellular signals that restrict the modification to appropriate situations. Nevertheless, many SUMO-specific ligases do not exhibit much target specificity, and—compared with the diversity of sumoylation substrates—their number is limited. This raises the question of how SUMO conjugation is controlled in vivo. We report here an unexpected mechanism by which sumoylation of the replication clamp protein, PCNA, from budding yeast is effectively coupled to S phase. We find that loading of PCNA onto DNA is a prerequisite for sumoylation in vivo and greatly stimulates modification in vitro. To our surprise, however, DNA binding by the ligase Siz1, responsible for PCNA sumoylation, is not strictly required. Instead, the stimulatory effect of DNA on conjugation is mainly attributable to DNA binding of PCNA itself. These findings imply a change in the properties of PCNA upon loading that enhances its capacity to be sumoylated

Nucleosome accessibility governed by the dimer/tetramer interface

Nucleosomes are multi-component macromolecular assemblies which present a formidable obstacle to enzymatic activities that require access to the DNA, e.g. DNA and RNA polymerases. The mechanism and pathway(s) by which nucleosomes disassemble to allow DNA access are not well understood. Here we present evidence from single molecule FRET experiments for a previously uncharacterized intermediate structural state before H2A–H2B dimer release, which is characterized by an increased distance between H2B and the nucleosomal dyad. This suggests that the first step in nucleosome disassembly is the opening of the (H3–H4)2 tetramer/(H2A–H2B) dimer interface, followed by H2A–H2B dimer release from the DNA and, lastly, (H3–H4)2 tetramer removal. We estimate that the open intermediate state is populated at 0.2–3% under physiological conditions. This finding could have significant in vivo implications for factor-mediated histone removal and exchange, as well as for regulating DNA accessibility to the transcription and replication machinery

Elective Caesarean Section Versus Vaginal Delivery In Preventing Vertical Hiv-1 Transmission: A Randomized Clinical Trial.

Background Results from observational studies suggest that caesarean-section delivery may reduce the risk of mother-to-child transmission of HIV-1 infection in comparison with vaginal delivery. We carried out a randomised clinical trial to address this issue and to assess the extent of postdelivery complications. Methods Eligible women were between 34 and 36 weeks of pregnancy, with a confirmed diagnosis of HIV-1 infection, and without an indication for caesarean-section delivery or a contraindication to this mode of delivery. Women were randomly assigned elective caesarean-section delivery at 38 weeks of pregnancy or vaginal delivery. An infant was classified as uninfected if he or she became negative for antibody to HIV-1 by age 18 months or was negative for virus by PCR or culture on at least two occasions, with no clinical, immunological, or viral evidence of infection. From 1993, to March, 1998, 436 women were randomised. Findings We present the results of an analysis updated to November, 1998, with data on the infection status of 370 infants. Three (1.8%) of 170 infants born to women assigned caesarean-section delivery were infected, compared with 21 (10.5%) of 200 born to women assigned vaginal delivery (p<0.001). Seven (3.4%) of 203 infants of women who actually gave birth by caesarean section were infected compared with 15 (10.2%) of 167 born vaginally (p=0.009). There were few postpartum complications and no serious adverse events in either group. Interpretation Our findings provide evidence that elective caesarean-section delivery significantly lowers the risk of mother-to-child transmission of HIV-1 infection without a significantly increased risk of complications for the mother

Breakthrough Cancer Pain: Preliminary Data of The Italian Oncologic Pain Multisetting Multicentric Survey (IOPS-MS)

Introduction: An ongoing national multicenter survey [Italian Oncologic Pain multiSetting Multicentric Survey (IOPS-MS)] is evaluating the characteristics of breakthrough cancer pain (BTP) in different clinical settings. Preliminary data from the first 1500 cancer patients with BTP enrolled in this study are presented here. Methods: Thirty-two clinical centers are involved in the survey. A diagnosis of BTP was performed by a standard algorithm. Epidemiological data, Karnofsky index, stage of disease, presence and sites of metastases, ongoing oncologic treatment, and characteristics of background pain and BTP and their treatments were recorded. Background pain and BTP intensity were measured. Patients were also questioned about BTP predictability, BTP onset (≤10 or >10 min), BTP duration, background and BTP medications and their doses, time to meaningful pain relief after BTP medication, and satisfaction with BTP medication. The occurrence of adverse reactions was also assessed, as well as mucosal toxicity. Results: Background pain was well controlled with opioid treatment (numerical rating scale 3.0 ± 1.1). Patients reported 2.5 ± 1.6 BTP episodes/day with a mean intensity of 7.5 ± 1.4 and duration of 43 ± 40 min; 977 patients (65.1%) reported non-predictable BTP, and 1076 patients (71.7%) reported a rapid onset of BTP (≤10 min). Higher patient satisfaction was reported by patients treated with fast onset opioids. Conclusions: These preliminary data underline that the standard algorithm used is a valid tool for a proper diagnosis of BTP in cancer patients. Moreover, rapid relief of pain is crucial for patients’ satisfaction. The final IOPS-MS data are necessary to understand relationships between BTP characteristics and other clinical variables in oncologic patients. Funding: Molteni Farmaceutici, Italy