Pheromone-encoding mRNA is transported to the yeast mating projection by specific RNP granules

Association of messenger RNAs with large complexes such as processing bodies (PBs) plays a pivotal role in regulating their translation and decay. Little is known about other possible functions of these assemblies. Exposure of haploid yeast cells, carrying mating type “a,” to “α pheromone” stimulates polarized growth resulting in a “shmoo” projection; it also induces synthesis of “a pheromone,” encoded by MFA2. In this paper, we show that, in response to α pheromone, MFA2 mRNA is assembled with two types of granules; both contain some canonical PB proteins, yet they differ in size, localization, motility, and sensitivity to cycloheximide. Remarkably, one type is involved in mRNA transport to the tip of the shmoo, whereas the other—in local translation in the shmoo. Normal assembly of these granules is critical for their movement, localization, and for mating. Thus, MFA2 mRNAs are transported to the shmoo tip, in complex with PB-like particles, where they are locally translated.     

Those dam-aged telomeres!

Telomere integrity plays a crucial role in the capacity for continuous cell proliferation. In some circumstances, shortened telomeres contribute to cell arrest or death, but in others, shortened telomeres may actually enhance the incidence and spectrum of tumors. Resolution of this apparent paradox requires a more detailed understanding of a non-functional telomere. Recent evidence reveals that critically shortened or uncapped telomeres share molecular hallmarks of damaged DNA. It is likely that the cellular response to this DNA damage, influenced by the nature of the damage itself, affects the outcome of loss of telomere function.     

Physiological role of neuropeptide Y in the regulation of the ascending phase of the peristaltic reflex

The physiological role of neuropeptide Y (NPY) and of specific NPY receptors in regulating the intestinal peristaltic reflex was examined in three-compartment flat-sheet preparations of rat colon. Graded muscle stretch or mucosal stimulation applied to the central compartment inhibited NPY release in the orad compartment where ascending contraction was measured. NPY and the Y1-receptor agonist [Leu31, Pro34]NPY inhibited, whereas the selective Y1-receptor antagonist BIBP 3226 augmented ascending contraction and substance P (SP) release in the orad compartment induced by muscle stretch or mucosal stimulation. Neither agonist nor antagonist had any effect on descending relaxation or VIP release in the caudad compartment. The Y2-receptor agonist NPY13-36 and antagonist BIIE 0246 had no effect on peptide release or mechanical response. The results indicate that suppression of a tonic inhibitory influence of NPY neurons on excitatory neurotransmitter release contributes substantially to the orad contractile phase of the peristaltic reflex. The effect of NPY on neurotransmitter release is mediated by Y1 receptors.     

Modulation of habit formation by levodopa in Parkinson's disease

Dopamine promotes the execution of positively reinforced actions, but its role for the formation of behaviour when feedback is unavailable remains open. To study this issue, the performance of treated/untreated patients with Parkinson's disease and controls was analysed in an implicit learning task, hypothesising dopamine-dependent adherence to hidden task rules. Sixteen patients on/off levodopa and fourteen healthy subjects engaged in a Go/NoGo paradigm comprising four equiprobable stimuli. One of the stimuli was defined as target which was first consistently preceded by one of the three non-target stimuli (conditioning), whereas this coupling was dissolved thereafter (deconditioning). Two task versions were presented: in a 'Go version', only the target cue required the execution of a button press, whereas non-target stimuli were not instructive of a response; in a 'NoGo version', only the target cue demanded the inhibition of the button press which was demanded upon any non-target stimulus. Levodopa influenced in which task version errors grew from conditioning to deconditioning: in unmedicated patients just as controls errors only rose in the NoGo version with an increase of incorrect responses to target cues. Contrarily, in medicated patients errors went up only in the Go version with an increase of response omissions to target cues. The error increases during deconditioning can be understood as a perpetuation of reaction tendencies acquired during conditioning. The levodopa-mediated modulation of this carry-over effect suggests that dopamine supports habit conditioning under the task demand of response execution, but dampens it when inhibition is required. However, other than in reinforcement learning, supporting dopaminergic actions referred to the most frequent, i. e., non-target behaviour. Since this is passive whenever selective actions are executed against an inactive background, dopaminergic treatment could in according scenarios contribute to passive behaviour in patients with Parkinson's disease.     

Analysis of Toxoplasma gondii surface antigen 2 gene (SAG2). Relevance of genotype I in clinical toxoplasmosis

Toxoplasma gondii is one of the most successful protozoan parasites given its ability to manipulate the immune system and establish a chronic infection. It is a parasite with a significant impact on human health, mainly in immunocompromised patients. In Europe and North America, only a few clonal genotypes (I, II and III) seem to be responsible for the vast majority of Toxoplasma infections. Surface antigen 2 gene (SAG2) has been extensively used for genotyping T. gondii isolates. The analysis of this locus reveals that in Northern hemisphere, human disease causing isolates are mainly type II, whereas T. gondii isolated from different animals are both type II and III. Since the immune response depends on parasite genotype, it seems relevant to characterize parasites producing human toxoplasmosis in different geographical areas. The growing information about the prevalent T. gondii genotypes in South America mostly refers to domestic animals. This is the first report of genetic characterization of T. gondii isolates from clinical samples in Chile, South America. All the samples analyzed corresponded to SAG2 type I isolates, and they differ from classic SAG2 type I by genetic polymorphisms. This study contributes to the scarce available information on T. gondii at South America, and reinforces an emerging concept suggesting that SAG2 type I, rather than II, parasites are a frequent cause of clinical toxoplasmosis in this continent.     

Tsg101 Is Recruited by a Late Domain of the Nucleocapsid Protein To Support Budding of Marburg Virus-Like Particles

The nucleoprotein NP of Marburg virus (MARV) is the major component of the viral nucleocapsid, which also consists of the viral proteins VP35, L, and VP30, as well as the viral genome. During virus assembly at the plasma membrane, the nucleocapsids are enwrapped by the major matrix protein VP40 and the viral envelope, which contains the transmembrane glycoprotein GP. Upon recombinant expression, VP40 alone is able to induce the formation and release of virus-like particles (VLPs) that closely resemble the filamentous morphology of MARV particles. Release of these VP40-induced VLPs is partially dependent on the cellular ESCRT machinery, which interacts with a late-domain motif in VP40. Coexpression with NP significantly enhances the budding of VP40-induced VLPs by an unknown mechanism. In the present study we analyzed the impact of late domains present in NP on the release of VLPs. We observed that the ESCRT I protein Tsg101 was recruited by NP into NP-induced inclusions in the perinuclear region. In the presence of VP40, NP was then recruited to VP40-positive membrane clusters and, in turn, recruited Tsg101 via a C-terminal PSAP late-domain motif in NP. This PSAP motif also mediated a dramatically enhanced incorporation of Tsg101 into VLPs, and its deletion significantly diminished the positive effect of NP on the release of VLPs. Taken together, these data indicate that NP enhances budding of VLPs by recruiting Tsg101 to the VP40-positive budding site through a PSAP late-domain motif.Virus budding is based on the coordinated interaction of viral proteins and supporting cellular proteins. While many viruses have been shown to use the cellular ESCRT machinery for budding, the means by which this machinery is usurped by different viruses varies (3). Viral matrix proteins are involved mainly in the recruitment of the cellular ESCRT proteins to the sites of viral budding; however, interaction between the respective matrix proteins and the ESCRT machinery is exerted by different late-domain motifs, which in turn recruit different ESCRT proteins. In the end, the outcomes are similar: viral budding is enhanced. The present study aims to understand a frequently observed phenomenon, i.e., that nucleocapsid proteins of viruses positively influence the budding activity of the viral matrix proteins. This observation has also been made with the nucleoprotein NP of Marburg virus (MARV).MARV and Ebola virus (EBOV) belong to the family Filoviridae, whose members are enveloped, nonsegmented, negative-strand RNA viruses of filamentous shape. Filoviruses cause sporadic outbreaks of severe hemorrhagic fever in humans and nonhuman primates in Central Africa, with mortality rates of up to 90% (10). No vaccines or antiviral treatments approved for human use are available to date; however, promising results were obtained in recent years with different experimental vaccine approaches (8).MARV particles are composed of seven structural proteins. The major nucleocapsid protein NP encapsidates the viral genome and, together with the polymerase L, the polymerase cofactor VP35, VP30, and the viral RNA, forms the viral nucleocapsid (1). The nucleocapsids are embedded in a matrix, composed of the matrix proteins VP40 and VP24, which connects the nucleocapsid with the lipid envelope. The only transmembrane glycoprotein, GP, is inserted in the lipid envelope (12, 27).Release of MARV particles takes place at the plasma membrane from sites where all subviral components have been recruited in a spatio-temporally orchestrated fashion. The details of this process are just beginning to be understood. It is known that MARV makes use of the cellular ESCRT machinery to support its own budding (16, 28). Consistent with this, downregulation of VPS4, a central player for the activity of the whole ESCRT machinery, impairs budding of MARV and EBOV severalfold (16, 19). The major player in the budding process of MARV is VP40, the intracellular expression of which results in the formation of peripheral VP40-positive membranous clusters beneath the plasma membrane and the release of filamentous virus-like particles (VLPs) that closely resemble MARV particles (12). VP40 is the only MARV protein that induces budding of filamentous particles and therefore is considered to be the driving force for virus release (11, 27). Further, VP40 is necessary for the redistribution of the nucleocapsids from cytoplasmic inclusions to the sites of particle assembly and budding (4) and finally for the recruitment of the surface glycoprotein GP from the trans-Golgi network into the VP40-positive peripheral clusters where budding takes place (21). As with the matrix proteins of many other enveloped viruses, VP40 contains a late-domain motif, specifically PPPY, that allows recruitment of an ESCRT-associated protein (i.e., Nedd 4), (2, 16, 29).Interestingly, coexpression of VP40 with NP results in enhanced release of VLPs, a phenomenon that was also observed for EBOV and the analogous proteins of other negative-strand RNA viruses (17-18, 26, 28). This suggests that cooperation between the respective nucleoproteins and matrix proteins is important for efficient budding; however, the underlying mechanism is unknown.Our analysis of the MARV NP amino acid sequence revealed that NP possesses several late-domain motifs, which may represent interaction targets for proteins of the cellular ESCRT machinery to enhance particle release. In the present study we show that a C-terminal Tsg101 interaction motif in NP mediated the recruitment of Tsg101 to the budding sites, resulting in increased release of VLPs.     

Sleep fragmentation in mentally retarded people decreases with increasing daylength in spring

We studied the sleep-wake behavior of mentally retarded people from late winter to early summer at 60 degrees N. During this time the daylength increased 8 h 51 min. The data were collected by observing the sleep-wake status of 293 subjects at 20-min intervals for five randomized 24h periods (= recording days). The intervals during which the individual recording days of the same order (1st, 2nd, etc.) were carried out, were called recording periods. Consequently, there were five recording periods, each containing 293 individual recording days. Even though there was overlap among the recording periods, the median daylength from one period to another increased approximately by 100 min. In the initial statistical analysis, the number of wake-sleep transitions was found to differ significantly among the five recording periods (Friedman test, p < 0.001). The mean ranks in the Friedman test suggested that the number of wake-sleep transitions was highest during the 1st and lowest during the 5th recording period. In further statistical analyses using a program for mixed effects regression analysis (MIXOR 2.0) it was found that the increase in daylength during the study period was associated with a simultaneous decrease of approximately 0.5 wake-sleep transitions in the whole study population (p < 0.001). The decrease in the number of wake-sleep transitions was significant only in the subgroups of subjects with a daylength change of more than 350 min between the 1st and 5th recording days (Wilcoxon tests, p < 0.005). This suggests that after a marked prolongation of the natural photoperiod, the reduction in sleep episodes was more probable than after smaller changes in daylength. It is concluded that the sleep of mentally retarded people living in a rehabilitation center at a northern latitude is more fragmented in winter than in early summer and that the change is related probably to the simultaneous increase in the length of the natural photoperiod. The sleep quality of persons living in institutional settings might be improved by increasing the intensity and/or duration of daily artificial light exposure during the darker seasons.     

Horizontal transmission of epizootic ulcerative syndrome (EUS)-associated virus in the snakehead Ophicephalus striatus under simulated natural conditions

Natural transmission of the epizootic ulcerative syndrome (EUS) was conducted on na?ve snakeheads Ophicephalus striatus (also known as Channa striata) kept (A) in aquifer water, (B) in lakewater, (C) cohabiting with EUS snakeheads in lakewater, and (D) cohabiting with apparently healthy snakeheads in lakewater during the 1994 to 1995 EUS season. The results showed that EUS-like lesions developed in 6 to 14 d among na?ve snakeheads cohabiting with EUS snakeheads and with apparently healthy snakeheads in lakewater (Treatments C and D). Among na?ve fish exposed to lakewater (Treatment B), similar lesions developed in 16 to 21 d, while na?ve fish in aquifer water (Treatment A) did not develop EUS-like lesions. EUS signs began as Grade I (slight) lesions that gradually progressed to Grades III-IV (severe) 3 to 5 d from lesion onset, similar to the naturally affected EUS fish. The virus was recovered from some but not all naturally EUS-affected snakeheads, snakeheads with healing lesions and apparently healthy snakeheads, but not from na?ve snakeheads. The results provide evidence of a waterborne horizontal transmission of the EUS-associated virus. This is the first report of a successful horizontal transmission of the EUS-associated virus from apparently healthy snakeheads to na?ve fish under natural conditions and of virus recovery in tissue culture from naturally exposed experimental fish.