Sequence Features and Transcriptional Stalling within Centromere DNA Promote Establishment of CENP-A Chromatin

Centromere sequences are not conserved between species, and there is compelling evidence for epigenetic regulation of centromere identity, with location being dictated by the presence of chromatin containing the histone H3 variant CENP-A. Paradoxically, in most organisms CENP-A chromatin generally occurs on particular sequences. To investigate the contribution of primary DNA sequence to establishment of CENP-A chromatin in vivo, we utilised the fission yeast Schizosaccharomyces pombe. CENP-ACnp1 chromatin is normally assembled on ∼10 kb of central domain DNA within these regional centromeres. We demonstrate that overproduction of S. pombe CENP-ACnp1 bypasses the usual requirement for adjacent heterochromatin in establishing CENP-ACnp1 chromatin, and show that central domain DNA is a preferred substrate for de novo establishment of CENP-ACnp1 chromatin. When multimerised, a 2 kb sub-region can establish CENP-ACnp1 chromatin and form functional centromeres. Randomization of the 2 kb sequence to generate a sequence that maintains AT content and predicted nucleosome positioning is unable to establish CENP-ACnp1 chromatin. These analyses indicate that central domain DNA from fission yeast centromeres contains specific information that promotes CENP-ACnp1 incorporation into chromatin. Numerous transcriptional start sites were detected on the forward and reverse strands within the functional 2 kb sub-region and active promoters were identified. RNAPII is enriched on central domain DNA in wild-type cells, but only low levels of transcripts are detected, consistent with RNAPII stalling during transcription of centromeric DNA. Cells lacking factors involved in restarting transcription-TFIIS and Ubp3-assemble CENP-ACnp1 on central domain DNA when CENP-ACnp1 is at wild-type levels, suggesting that persistent stalling of RNAPII on centromere DNA triggers chromatin remodelling events that deposit CENP-ACnp1. Thus, sequence-encoded features of centromeric DNA create an environment of pervasive low quality RNAPII transcription that is an important determinant of CENP-ACnp1 assembly. These observations emphasise roles for both genetic and epigenetic processes in centromere establishment

Inflammatory resolution: New opportunities for drug discovery

Treatment of inflammatory diseases today is largely based on interrupting the synthesis or action of mediators that drive the host’s response to injury. Non-steroidal anti-inflammatories, steroids and antihistamines, for instance, were developed on this basis. Although such small-molecule inhibitors have provided the main treatment for inflammatory arthropathies and asthma, they are not without their shortcomings. This review offers an alternative approach to the development of novel therapeutics based on the endogenous mediators and mechanisms that switch off acute inflammation and bring about its resolution. It is thought that this strategy will open up new avenues for the future management of inflammation-based diseases

Laparoscopic antireflux surgery in patients with throat symptoms: A word of caution

BackgroundA subset of patients undergoing laparoscopic fundoplication presents with atypical throat symptoms, and the benefit of surgery in these patients is debated. These patients can present with throat symptoms alone or in combination with typical reflux symptoms. We evaluated the clinical outcome in these patients and compared their outcomes with a larger group of patients who did not have throat symptoms before fundoplication.MethodsOutcome data for 893 consecutive patients who underwent a laparoscopic fundoplication from January 2002 to June 2008 were collected prospectively and managed on a database. Ninety-three patients with atypical throat symptoms were identified, and divided into subgroups with (n=66) and without (n=27) typical reflux symptoms (heartburn and/or regurgitation), and outcomes were compared with patients (n=800) who didn't have throat symptoms. Symptoms were assessed with analog symptom scores for heartburn and dysphagia, as well as satisfaction with the surgical outcome. Case records for patients with throat symptoms were also reviewed to obtain more detail about specific throat symptoms and their resolution.ResultsCough was the commonest atypical symptom, followed by sore throat. Heartburn scores improved following surgery in all patient groups. Dysphagia was more common 3 months after surgery in patients without throat symptoms, although there were no differences for dysphagia at later follow-up. Following surgery satisfaction scores were highest in patients with atypical throat symptoms who also had typical reflux symptoms, and the scores were lowest in patients who only had atypical throat symptoms. Nearly twice as many patients who had throat and reflux symptoms reported improvement or resolution of symptoms, compared to patients who only had throat symptoms.ConclusionsFundoplication achieves a good outcome in patients with atypical throat symptoms who also report typical symptoms of reflux. However, surgeons should be cautious about operating on the subgroup of patients with objective evidence of gastroesophageal reflux who describe throat symptoms but do not report heartburn or regurgitation. In this subgroup, expectations of a good outcome should be minimized.Dharmendran Ratnasingam, Tanya Irvine, Sarah K. Thompson, David I. Watso

Predictors of Unprotected Sex Among Female Sex Workers in Madagascar: Comparing Semen Biomarkers and Self-Reported Data

Research on the determinants of condom use and condom non-use generally has relied on self-reported data with questionable validity. We identified predictors of recent, unprotected sex among 331 female sex workers in Madagascar using two outcome measures: self-reports of unprotected sex within the past 48 h and detection of prostate-specific antigen (PSA), a biological marker of recent semen exposure. Multivariable logistic regression revealed that self-reported unprotected sex was associated with three factors: younger age, having a sipa (emotional partner) in the prior seven days, and no current use of hormonal contraception. The sole factor related to having PSA detected was prevalent chlamydial infection (adjusted odds ratio, 4.5; 95% confidence interval, 2.0–10.1). Differences in predictors identified suggest that determinants of unprotected sex, based on self-reported behaviors, might not correlate well with risk of semen exposure. Caution must be taken when interpreting self-reported sexual behavior measures or when adjusting for them in analyses evaluating interventions for the prevention of HIV/STIs