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<jats:p> The leaf sucrose transporter SUT1 is essential for phloem loading and long-distance transport of assimilates. Both SUT1 messenger RNA (mRNA) and protein were shown to be diurnally regulated and to have high turnover rates. SUT1 protein was detected by immunolocalization in plasma membranes of enucleate sieve elements (SEs) in tobacco, potato, and tomato. Analysis by in situ hybridization showed that SUT1 mRNA localizes mainly to the SE and is preferentially associated with plasmodesmata. Antisense inhibition of <jats:italic>SUT1</jats:italic> expression under control of a companion cell (CC)-specific promoter indicated synthesis of <jats:italic>SUT1</jats:italic> mRNA in the CC. These results provide evidence for targeting of plant endogenous mRNA and potentially SUT1 protein through phloem plasmodesmata and for sucrose loading at the plasma membrane of SE. </jats:p>

<jats:p> A gene encoding a zinc finger protein of the <jats:italic>Snail</jats:italic> family, <jats:italic>cSnR</jats:italic> , is expressed in the right-hand lateral mesoderm during normal chick development. Antisense disruption of <jats:italic>cSnR</jats:italic> function during the hours immediately preceding heart formation randomized the normally reliable direction of heart looping and subsequent embryo torsion. Implanted ectopic sources of intercellular signal proteins that are involved in establishing normal left-right information randomized the handedness of heart development and also altered the asymmetry of <jats:italic>cSnR</jats:italic> expression. <jats:italic>cSnR</jats:italic> thus appears to act downstream of these signals, or perhaps in parallel with the latest expressed of them, the Nodal protein, in controlling the anatomical asymmetry. </jats:p>

<jats:p> Formate dehydrogenase H from <jats:italic>Escherichia coli</jats:italic> contains selenocysteine (SeCys), molybdenum, two molybdopterin guanine dinucleotide (MGD) cofactors, and an Fe <jats:sub>4</jats:sub> S <jats:sub>4</jats:sub> cluster at the active site and catalyzes the two-electron oxidation of formate to carbon dioxide. The crystal structures of the oxidized [Mo(VI), Fe <jats:sub>4</jats:sub> S <jats:sub>4(ox)</jats:sub> ] form of formate dehydrogenase H (with and without bound inhibitor) and the reduced [Mo(IV), Fe <jats:sub>4</jats:sub> S <jats:sub>4(red)</jats:sub> ] form have been determined, revealing a four-domain αβ structure with the molybdenum directly coordinated to selenium and both MGD cofactors. These structures suggest a reaction mechanism that directly involves SeCys <jats:sup>140</jats:sup> and His <jats:sup>141</jats:sup> in proton abstraction and the molybdenum, molybdopterin, Lys <jats:sup>44</jats:sup> , and the Fe <jats:sub>4</jats:sub> S <jats:sub>4</jats:sub> cluster in electron transfer. </jats:p>

<jats:p>The small guanosine triphosphatase (GTPase) Rho is implicated in the formation of stress fibers and focal adhesions in fibroblasts stimulated by extracellular signals such as lysophosphatidic acid (LPA). Rho-kinase is activated by Rho and may mediate some biological effects of Rho. Microinjection of the catalytic domain of Rho-kinase into serum-starved Swiss 3T3 cells induced the formation of stress fibers and focal adhesions, whereas microinjection of the inactive catalytic domain, the Rho-binding domain, or the pleckstrin-homology domain inhibited the LPA-induced formation of stress fibers and focal adhesions. Thus, Rho-kinase appears to mediate signals from Rho and to induce the formation of stress fibers and focal adhesions.</jats:p>

<jats:p> The molecular mechanisms that link cell-cycle controls to the mitotic apparatus are poorly understood. A component of the <jats:italic>Saccharomyces cerevisiae</jats:italic> spindle, Ase1, was observed to undergo cell cycle-specific degradation mediated by the cyclosome, or anaphase promoting complex (APC). Ase1 was degraded when cells exited from mitosis and entered G <jats:sub>1</jats:sub> . Inappropriate expression of stable Ase1 during G <jats:sub>1</jats:sub> produced a spindle defect that is sensed by the spindle assembly checkpoint. In addition, loss of <jats:italic>ASE1</jats:italic> function destabilized telophase spindles, and expression of a nondegradable Ase1 mutant delayed spindle disassembly. APC-mediated proteolysis therefore appears to regulate both spindle assembly and disassembly. </jats:p>

<jats:p> In yeast, an overlapping set of mitogen-activated protein kinase (MAPK) signaling components controls mating, haploid invasion, and pseudohyphal development. Paradoxically, a single downstream transcription factor, Ste12, is necessary for the execution of these distinct programs. Developmental specificity was found to require a transcription factor of the TEA/ATTS family, Tec1, which cooperates with Ste12 during filamentous and invasive growth. Purified derivatives of Ste12 and Tec1 bind cooperatively to enhancer elements called filamentation and invasion response elements (FREs), which program transcription that is specifically responsive to the MAPK signaling components required for filamentous growth. An FRE in the <jats:italic>TEC1</jats:italic> promoter functions in a positive feedback loop required for pseudohyphal development. </jats:p>

<jats:p> The role of transforming growth factor-β (TGF-β) in long-term synaptic facilitation was examined in isolated <jats:italic>Aplysia</jats:italic> ganglia. Treatment with TGF-β1 induced long-term facilitation (24 and 48 hours), but not short-term (5 to 15 minutes) or intermediate-term (2 to 4 hours) facilitation. The long-term effects of TGF-β1 were not additive with those of serotonin. Moreover, serotonin-induced facilitation was blocked by an inhibitor of TGF-β. Thus, activation of TGF-β may be part of the cascade of events underlying long-term sensitization, consistent with the hypothesis that signaling molecules that participate in development also have roles in adult neuronal plasticity. </jats:p>

<jats:p>A complementary DNA clone has been isolated that encodes a coxsackievirus and adenovirus receptor (CAR). When transfected with CAR complementary DNA, nonpermissive hamster cells became susceptible to coxsackie B virus attachment and infection. Furthermore, consistent with previous studies demonstrating that adenovirus infection depends on attachment of a viral fiber to the target cell, CAR-transfected hamster cells bound adenovirus in a fiber-dependent fashion and showed a 100-fold increase in susceptibility to virus-mediated gene transfer. Identification of CAR as a receptor for these two unrelated and structurally distinct viral pathogens is important for understanding viral pathogenesis and has implications for therapeutic gene delivery with adenovirus vectors.</jats:p>