Werner syndrome (WS) is a rare human premature aging disease caused by mutations in the gene encoding the RecQ helicase WRN. In addition to the aging features, this disorder is marked by genomic instability, associated with an elevated incidence of cancer. Several lines of evidence suggest that telomere dysfunction is associated with the aging phenotype of the syndrome; however, the origin of the genomic instability observed in WS cells and the reason for the high incidence of cancer in WS have not been established. We previously proposed that WRN helicase activity was necessary to prevent dramatic telomere loss during DNA replication. Here we demonstrate that replication-associated telomere loss is responsible for the chromosome fusions found in WS fibroblasts. Moreover, using metaphase analysis we show that telomere elongation by telomerase can significantly reduce the appearance of new chromosomal aberrations in cells lacking WRN, similar to complementation of WS cells with WRN. Our results suggest that the genome instability in WS cells depends directly on telomere dysfunction, linking chromosome end maintenance to chromosomal aberrations in this disease.cancer ͉ WRN ͉ genome instability ͉ aging

The adenovirus (Ad) E1b55K and E4orf6 gene products assemble an E3 ubiquitin ligase complex that promotes degradation of cellular proteins. Among the known substrates are p53 and the Mre11-Rad50-Nbs1 (MRN) complex. Since members of the RecQ helicase family function together with MRN in genome maintenance, we investigated whether adenovirus affects RecQ proteins. We show that Bloom helicase (BLM) is degraded during adenovirus type 5 (Ad5) infection. BLM degradation is mediated by E1b55K/E4orf6 but is independent of MRN. We detected BLM localized at discrete foci around viral replication centers. These studies identify BLM as a new substrate for degradation by the adenovirus E1b55K/E4orf6 complex.

Bronchopulmonary dysplasia, a common complication of prematurity, is characterized by inadequate alveolarization. The process of alveolarization, by which the lung forms mature gas-exchanging units, is not well understood. In mice, alveolarizaion occurs during postnatal days four through twelve, when the formation of secondary septa creates thin walled alveoli. The purpose of this study was to investigate the genes involved in this process. RNA was isolated from dissected tips of secondary septa and whole lung tissue of day six postnatal mouse lung. The tips of secondary septa were obtained via laser capture microscopy of frozen sections. Total RNA was isolated from the tip and whole lung samples and amplified in the same manner. Affymetrix gene profiling was then performed, using mouse U74Av2 GeneChips. The signal for galectin-1 mRNA was six fold higher in the secondary septal tips than in whole lung tissue (pϽ0.05). Galectins, or S-type lectins, are beta-galactosidebinding proteins involved in the regulation of cell proliferation, differentiation and apoptosis. Galectin-1 is a homodimer of two 14 kDa subunits. It is the most abundant galectin in the lung. To confirm the relative abundance of galectin-1 in secondary septal tips versus whole lung, immunostaining of sections of day six postnatal and adult mouse lung tissue was performed. Staining for galectin-1 was concentrated in the tips of the secondary septa in the day six postnatal tissue. Furthermore, staining was dramatically increased in the day six mouse lung tissue when compared to staining levels in the adult lung sections. Immunoblot analysis of lung homogenates obtained at different stages of lung development demonstrated that a peak of galectin-1 expression occurs at postnatal days six and twelve, corresponding to the time of alveolarization. The increased expression of galectin-1 at the site and time of ongoing alveolarization suggests that it may play a role in this important aspect of lung development. Supported by NIH grants HL-62861 and HL-07638. SU1498 INHIBITS ALVEOLARIZATION IN NEWBORN MICE.Cho SJ, George CS, Snyder JM, Acarregui MJ. Carver College of Medicine, Univ. of Iowa, Iowa City, IA BACKGROUND: Bronchopulmonary dysplasia (BPD) in premature infants is characterized by inhibited alveolarization and vasculogenesis. Inhibitors of angiogenesis induce emphysema in newborn rats resulting in a phenotype similar to BPD in premature infants. Our goal was to generate a mouse model of inhibited alveolarization that could be employed to explore the mechanisms resulting in, and interventions for BPD. SU1498 is a commercially available compound that inhibits vascular endothelial growth factor receptors. METHODS: Three day old C3H/HeNHsd mice were injected with a single dose of SU1498 (30mg/kg, SC). Lungs of control (sham-injected) and treated mice were inflation fixed on postnatal day 21. Tissue sections were mounted and morphometric analysis was performed to determine the volume density (VD) of air space, tissue, large blood vessels, conducting air...