Long-term outcome after surgery in a patient with intestinal Behçet’s disease complicated by myelodysplastic syndrome and trisomy 8

Behçet’s disease (BD) is a multisystem inflammatory disease of unknown origin. Rarely, BD occurs together with myelodysplastic syndrome (MDS). Interestingly, it is speculated that these are not simple coexistence but that the etiology of intestinal BD is at least partly derived from MDS itself. Furthermore, there is a relationship between MDS in patients with intestinal BD and trisomy 8. Immunosuppressive agents alone are insufficient to control MDS-associated BD, and many of these patients die of infection or hemorrhage. Surgery is considered for intestinal BD patients who are unresponsive to medical treatment or those with bowel complications such as perforation or persistent bleeding. We report a case of intestinal BD associated with MDS and trisomy 8. The patient was unresponsive to oral steroids and immunosuppressive treatment; the patient improved by surgical repair of a bowel perforation. Five years after the surgery, the patient is free of recurrence and not on medication. Our experience suggests that surgery may provide an effective therapeutic option for the treatment of MDS-related BD.

ChIP-on-chip analysis of DNA topoisomerases.

Here we describe an adapted ChIP-on-chip protocol for the analysis of DNA topoisomerase chromosomal binding in Saccharomyces cerevisiae cells. The ChIP-on-chip technique is based on the immunoprecipitation of crosslinked chromatin (ChIP, chromatin immunoprecipitation), followed by DNA amplification and hybridization to high-density oligonucleotide arrays (Chip). Comparison of the signal intensities of immunoprecipitated and control fractions provides a measurement of the protein-DNA association along entire genomes. ChIP-on-chip analysis of DNA topoisomerase binding to chromosomal DNA opens a window to the understanding of the in vivo contribution of these enzymes to the different DNA transactions taking place concomitantly within the context of the highly organized eukaryotic genome. Chromosomal binding profiles obtained from synchronized cells allow scoring the temporal and spatial restriction of these enzymes at different cell cycle stages. By using this approach, novel aspects of DNA topoisomerase function in chromosome metabolism might be unmasked.

Top1- and Top2-mediated topological transitions at replication forks ensure fork progression and stability and prevent DNA damage checkpoint activation.

DNA topoisomerases solve topological problems during chromosome metabolism. We investigated where and when Top1 and Top2 are recruited on replicating chromosomes and how their inactivation affects fork integrity and DNA damage checkpoint activation. We show that, in the context of replicating chromatin, Top1 and Top2 act within a 600-base-pair (bp) region spanning the moving forks. Top2 exhibits additional S-phase clusters at specific intergenic loci, mostly containing promoters. TOP1 ablation does not affect fork progression and stability and does not cause activation of the Rad53 checkpoint kinase. top2 mutants accumulate sister chromatid junctions in S phase without affecting fork progression and activate Rad53 at the M-G1 transition. top1 top2 double mutants exhibit fork block and processing and phosphorylation of Rad53 and gamma H2A in S phase. The exonuclease Exo1 influences fork processing and DNA damage checkpoint activation in top1 top2 mutants. Our data are consistent with a coordinated action of Top1 and Top2 in counteracting the accumulation of torsional stress and sister chromatid entanglement at replication forks, thus preventing the diffusion of topological changes along large chromosomal regions. A failure in resolving fork-related topological constrains during S phase may therefore result in abnormal chromosome transitions, DNA damage checkpoint activation, and chromosome breakage during segregation.