Mechanism and a Peptide Motif for Targeting Peripheral Proteins to the Yeast Inner Nuclear Membrane

Trm1 is a tRNA specific m₂²G methyltransferase shared by nuclei and mitochondria in Saccharomyces cerevisiae . In nuclei, Trm1 is peripherally associated with the inner nuclear membrane (INM). We investigated the mechanism delivering/tethering Trm1 to the INM. Analyses of mutations of the Ran pathway and nuclear pore components showed that Trm1 accesses the nucleoplasm via the classical nuclear import pathway. We identified a Trm1 cis-acting sequence sufficient to target passenger proteins to the INM. Detailed mutagenesis of this region uncovered specific amino acids necessary for authentic Trm1 to locate at the INM. The INM information is contained within a sequence of less than 20 amino acids, defining the first motif for addressing a peripheral protein to this important subnuclear location. The combined studies provide a multi-step process to direct Trm1 to the INM: (i) translation in the cytoplasm; (ii) Ran-dependent import into the nucleoplasm; and (iii) redistribution from the nucleoplasm to the INM via the INM motif. Furthermore, we demonstrate that the Trm1 mitochondrial targeting and nuclear localization signals are in competition with each other, as Trm1 becomes mitochondrial if prevented from entering the nucleus.     

Advancing uracil-excision based cloning towards an ideal technique for cloning PCR fragments

The largely unused uracil-excision molecular cloning technique has excellent features in most aspects compared to other modern cloning techniques. Its application has, however, been hampered by incompatibility with proof-reading DNA polymerases. We have advanced the technique by identifying PfuCx as a compatible proof-reading DNA polymerase and by developing an improved vector design strategy. The original features of the technique, namely simplicity, speed, high efficiency and low cost are thus combined with high fidelity as well as a transparent, simple and flexible vector design. A comprehensive set of vectors has been constructed covering a wide range of different applications and their functionality has been confirmed.     

Modeling the long-term effect of PCBs on Everglades fish communities

Fish communities are regularly exposed to a large number of natural and synthetic toxic chemicals, whose harmful effects, both short-term and long-term, need to be studied. Mathematical simulation models are known to be useful tools in the assessment of both acute and chronic effects. A time-concentration-effect model has been developed to assess the long-term effect of PCBs on multi generations of fish communities in the Florida Everglades. The term fish is used here generically to refer to five functional fish groups (FGs), two having small and two having large adult size, and a crustacean (crayfish), each of which are further composed of several age classes. Several contaminant concentration scenarios are analyzed in the simulations, subject to mortality and hatchability failure. The model predicts the population response time series for each FG, based upon exposure concentration and duration. Model results indicate that a concentration of 0.1 gl^–1 could have adverse effects on survival and reproduction success for Everglades fish communities. For comparison, the USEPA has stipulated a standard of 0.014 gl^–1 for the protection of freshwater fish from chronic effects and a standard of 1.0 gl^–1 from acute effects. Hopefully, the model may be further developed to assist in the formulation of policy or regulations concerning aquatic ecological risk to protect the aquatic ecosystem of the Everglades.     

Nucleotide insertion opposite a cis-syn thymine dimer by a replicative DNA polymerase from bacteriophage T7

Ultraviolet-induced DNA damage poses a lethal block to replication. To understand the structural basis for this, we determined crystal structures of a replicative DNA polymerase from bacteriophage T7 in complex with nucleotide substrates and a DNA template containing a cis-syn cyclobutane pyrimidine dimer (CPD). When the 3' thymine is the templating base, the CPD is rotated out of the polymerase active site and the fingers subdomain adopts an open orientation. When the 5' thymine is the templating base, the CPD lies within the polymerase active site where it base-pairs with the incoming nucleotide and the 3' base of the primer, while the fingers are in a closed conformation. These structures reveal the basis for the strong block of DNA replication that is caused by this photolesion.     

Molecular and ecological study of <Emphasis Type="Italic">Eryngium</Emphasis> species in Syria

Eryngium L. species growing in Syria were characterized using morphological, geographical and molecular analyses (IRAP and RAPD). Eight Eryngium L. species have been determined to exist in Syria. E. glomeratum, E. campestre and E. falcatum were found to grow in the mountain regions. E. creticum and E. desertorum were found to grow in variant environments: mountains, semidesert and saline environments, which indicate their wide range of adaptation and tolerance to abiotic stresses.     

Unusual labial glands in snakes of the genus Geophis Wagler, 1830 (Serpentes: Dipsadinae)

Geophis belongs to the goo‐eating dipsadine assemblage of snakes that are known to feed exclusively on earthworms, snails, and slugs. Although the unusual feeding strategies of the goo‐eating dipsadines are well known (but poorly documented), little attention has been paid to their internal anatomy. Here, we describe a new and noteworthy morphological and histochemical condition of the infralabial glands in three species of Geophis (G. brachycephalus, G. nasalis and G. semidoliatus), all earthworm feeders. Their infralabial glands are constituted of two distinct parts: an anterolateral portion composed of mucous and seromucous cells that stretches from the tip of the dentary to the corner of the mouth, and a tubular posteromedial portion that is exclusively seromucous. The anterolateral portion receives fibers of the levator anguli oris muscle that attaches on its posterodorsal extremity while the posteromedial portion extends posteriorly to the corner of the mouth where it receives fibers of the adductor mandibulae externus medialis muscle. Furthermore, the posteromedial portion of the infralabial gland is constituted by large acini filled with secretion that is periodic acid‐Schiff positive. These acini release their secretion directly into a large lumen located in the middle of the glandular portion. In the three species examined, the supralabial glands show a traditional configuration, being constituted of mucous and seromucous cells and retaining an enlarged part in its caudal region that resembles a Duvernoy's gland. The presence in Geophis of an expanded lumen in part of the infralabial gland that is compressed by an adjacent muscle suggests a more specialized role for the secretion produced by these glands that may not be related to envenomation but rather to prey transport and mucus control. J. Morphol. 275:87–99, 2014. © 2013 Wiley Periodicals, Inc.     

Acceptance of trial of labor after cesarean (Tolac) among obstetricians in the Western Region of Saudi Arabia: A cross-sectional study

BackgroundBabies to women eligible for trial of labor after a cesarean (TOLAC) are sometimes delivered by cesarean section (CS). To obtain clinicians’ attitudes and beliefs about TOLAC, this study was designed to investigate the views of clinicians when advising TOLAC-eligible pregnant women about TOLAC, and to explore their reasons in favor of or against TOLAC.MethodsInterviews were carried out individually (face-to-face) with clinicians using a specially designed questionnaire to collect data from obstetricians in the Western Region of Saudi. Regression analysis was used as appropriate.ResultsAmong the 183 obstetricians included in the current study, approximately 79.2% were against offering TOLAC. However, most of the physicians (89.1%) were in favor of offering TOLAC to patients who had had a successful vaginal birth after CS. significant associations were found between physicians’ opposition to TOLAC and medical and most non-medical factors.ConclusionClinicians should recognize that the critical role they play in the delivery decision-making process and in boosting women’s confidence in TOLAC may be key to increasing the rate of TOLAC.