Werner syndrome is a human premature aging disorder displaying cellular defects associated with telomere maintenance including genomic instability, premature senescence, and accelerated telomere erosion. The yeast homologue of the Werner protein (WRN), Sgs1, is required for recombination-mediated lengthening of telomeres in telomerase-deficient cells. In human cells, we report that WRN co-localizes and physically interacts with the critical telomere maintenance protein TRF2. This interaction is mediated by the RecQ conserved Cterminal region of WRN. In vitro, TRF2 demonstrates high affinity for WRN and for another RecQ family member, the Bloom syndrome protein (BLM). TRF2 interaction with either WRN or BLM results in a notable stimulation of their helicase activities. Furthermore, the WRN and BLM helicases, partnered with replication protein A, actively unwind long telomeric duplex regions that are pre-bound by TRF2. These results suggest that TRF2 functions with WRN, and possibly BLM, in a common pathway at telomeric ends.

ELABELA (ELA) was recently discovered as a novel endogenous ligand of the apelin receptor (APJ), a G protein-coupled receptor. ELA signaling was demonstrated to be crucial for normal heart and vasculature development during embryogenesis. We delineate here ELA's structure-activity relationships and report the identification of analogue 3 (ELA(19-32)), a fragment of ELA that binds to APJ, activates the Gαi1 and β-arrestin-2 signaling pathways, and induces receptor internalization similarly to its parent endogenous peptide. An alanine scan performed on 3 revealed that the C-terminal residues are critical for binding to APJ and signaling. Finally, using isolated-perfused hearts and in vivo hemodynamic and echocardiographic measurements, we demonstrate that ELA and 3 both reduce arterial pressure and exert positive inotropic effects on the heart. Altogether, these results present ELA and 3 as potential therapeutic options in managing cardiovascular diseases.

Our data suggest that activation of the ERK pathway functions to protect pancreatic tumor cells from apoptosis as well as to regulate their progression in the cell cycle.

Our data suggest that activation of the ERK pathway functions to protect pancreatic tumor cells from apoptosis as well as to regulate their progression in the cell cycle.

DNA loops that juxtapose the promoter and terminator regions of RNA polymerase II-transcribed genes have been identified in yeast and mammalian cells. Loop formation is transcription-dependent and requires components of the pre-mRNA 39-end processing machinery. Here we report that looping at the yeast GAL10 gene persists following a cycle of transcriptional activation and repression. Moreover, GAL10 and a GAL1p-SEN1 reporter undergo rapid reactivation kinetics following a cycle of activation and repression-a phenomenon defined as ''transcriptional memory''-and this effect correlates with the persistence of looping. We propose that gene loops facilitate transcriptional memory in yeast.Supplemental material is available at http://www.genesdev.org.

Werner syndrome is a human disorder characterized by premature aging, genomic instability, and abnormal telomere metabolism. The Werner syndrome protein (WRN) is the only known member of the RecQ DNA helicase family that contains a 3 3 5-exonuclease. However, it is not known whether both activities coordinate in a biological pathway. Here, we describe DNA structures, forked duplexes containing telomeric repeats, that are substrates for the simultaneous action of both WRN activities. We used these substrates to study the interactions between the WRN helicase and exonuclease on a single DNA molecule. WRN helicase unwinds at the forked end of the substrate, whereas the WRN exonuclease acts at the blunt end. Progression of the WRN exonuclease is inhibited by the action of WRN helicase converting duplex DNA to single strand DNA on forks of various duplex lengths. The WRN helicase and exonuclease act in concert to remove a DNA strand from a long forked duplex that is not completely unwound by the helicase. We analyzed the simultaneous action of WRN activities on the long forked duplex in the presence of the WRN protein partners, replication protein A (RPA), and the Ku70/80 heterodimer. RPA stimulated the WRN helicase, whereas Ku stimulated the WRN exonuclease. In the presence of both RPA and Ku, the WRN helicase activity dominated the exonuclease activity. Werner syndrome (WS)1 is a human autosomal recessive disorder characterized by early onset of premature aging and an increased incidence of cancer (1, 2). The gene (WRN) defective in WS (3) encodes a 1432-amino acid protein (WRN) that has ATPase, 3Ј 3 5Ј-helicase and 3Ј 3 5Ј-exonuclease activities (4 -8). WRN (WRNp) is a member of the RecQ family of DNA helicases, which also includes yeast Saccharomyces cerevisiae Sgs1 (9, 10), and four other human members, including the genes mutated in Bloom's Syndrome (BLM) (11) and in Rothmund-Thomson's Syndrome (RecQL4) (12). Bloom's Syndrome and Rothmund-Thomson's Syndrome resemble WS, in that they are characterized by a predisposition to malignancies and increased genomic instability (13). Therefore, the RecQ helicases appear to play important biological roles, most probably relating to DNA metabolism.Cells from patients with WS show premature replicative senescence and an extended S-phase compared with cells derived from normal individuals (14, 15). WS cells are also hypersensitive to selected DNA-damaging agents including 4-nitroquinoline-1-oxide (16) and exhibit increased genomic instability indicated by elevated levels of DNA deletions, translocations, and chromosomal breaks (17, 18). These observations and previous studies support a role for WRN in replication and/or anti-recombination pathways (13,19). Furthermore, WS cells display some defects in telomere metabolism, including increased rates of telomere shortening (20) and deficiencies in repair at telomeres (21). The expression of telomerase in WS cell lines prevented premature replicative senescence (22) and partially reversed the hypersensitivity to 4NQO (23). Thes...

The transcription-coupled repair (TCR) pathway preferentially repairs DNA damage located in the transcribed strand of an active gene. To gain insight into the coupling mechanism between transcription and repair, we have set up an in vitro system in which we isolate an elongating RNA pol IIO, which is stalled in front of a cisplatin adduct. This immobilized RNA pol IIO is used as 'bait' to sequentially recruit TFIIH, XPA, RPA, XPG and XPF repair factors in an ATP-dependent manner. This RNA pol IIO/repair complex allows the ATP-dependent removal of the lesion only in the presence of CSB, while the latter does not promote dual incision in an XPC-dependent nucleotide excision repair reaction. In parallel to the dual incision, the repair factors also allow the partial release of RNA pol IIO. In this 'minimal TCR system', the RNA pol IIO can effectively act as a loading point for all the repair factors required to eliminate a transcription-blocking lesion.

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