An RNA-binding protein recognizes a mammalian selenocysteine insertion sequence element required for cotranslational incorporation of selenocysteine.

In mammalian selenoprotein mRNAs, the recognition of UGA as selenocysteine requires selenocysteine insertion sequence (SECIS) elements that are contained in a stable stem-loop structure in the 3' untranslated region (UTR). In this study, we investigated the SECIS elements and cellular proteins required for selenocysteine insertion in rat phospholipid hydroperoxide glutathione peroxidase (PhGPx). We developed a translational readthrough assay for selenoprotein biosynthesis by using the gene for luciferase as a reporter. Insertion of a UGA or UAA codon into the coding region of luciferase abolished luciferase activity. However, activity was restored to the UGA mutant, but not to the UAA mutant, upon insertion of the PhGPx 3' UTR. The 3' UTR of rat glutathione peroxidase (GPx) also allowed translational readthrough, whereas the PhGPx and GPx antisense 3' UTRs did not. Deletion of two conserved SECIS elements in the PhGPx 3' UTR (AUGA in the 5' stem or AAAAC in the terminal loop) abolished readthrough activity. UV cross-linking studies identified a 120-kDa protein in rat testis that binds specifically to the sense strands of the PhGPx and GPx 3' UTRs. Direct cross-linking and competition experiments with deletion mutant RNAs demonstrated that binding of the 120-kDa protein requires the AUGA SECIS element but not AAAAC. Point mutations in the AUGA motif that abolished protein binding also prevented readthrough of the UGA codon. Our results suggest that the 120-kDa protein is a significant component of the mechanism of selenocysteine incorporation in mammalian cells.     

Variation in the ribosomal internal transcribed spacers and 5.8S rDNA among five species of Acropora (Cnidaria; Scleractinia): patterns of variation consistent with reticulate evolution

The ITS sequences of Acropora spp. are the shortest so far identified in any metazoan and are among the shortest seen in eukaryotes; ITS1 was 70-80 bases, and ITS2 was 100-112 bases. The ITS sequences were also highly variable, but base composition and secondary structure prediction indicate that divergent sequence variants are unlikely to be pseudogenes. The pattern of variation was unusual in several other respects: (1) two distinct ITS2 types were detected in both A. hyacinthus and A. cytherea, species known to hybridize in vitro with high success rates, and a putative intermediate ITS2 form was also detected in A. cytherea; (2) A. valida was found to contain highly (29%) diverged ITS1 variants; and (3) A. longicyathus contained two distinct 5.8S rDNA types. These data are consistent with a reticulate evolutionary history for the genus Acropora.      

The migration route and behaviour of Eastern Curlews Numenius madagascariensis

Eastern Curlews Numenius madagascariensis were satellite-tracked onto breeding grounds in north-eastern Russia from south-eastern Queensland over a distance of 12 000 km. They made initial non-stop, long distance flights across the Western Pacific Ocean towards the coastlines of China and Korea followed by shorter flights, over a period of more than a month. The return journey involved a major flight-leg as well, south from the Yellow Sea region. Many birds attempted to migrate but returned to the non-breeding grounds over periods of up to several months. Islands of the Western Pacific region, the southern coastline of New Guinea and north-eastern coastline of Australia are important, particularly for birds that stop migrating. Eastern Curlews that stopped migrating generally survived, which suggests that the species has adapted to deal with adverse conditions en route and/or a physical inability to complete the migration. Such a capacity is perhaps characteristic of a large wader with low annual mortality.     

Evidence against somatic association in hexaploid wheat

In mitotic interphase nuclei, nucleolus-organizing regions of homologous chromosomes lay no closer to each other than nucleolus-organizing regions of non-homologous chromosomes. — Mitotic metaphase studies of distances between satellites and also between telocentrics showed no greater nearness of homologues than of non-homologues. — These studies fail to support the concept of somatic association in hexaploid wheat.     

Nucleolar behaviour in Triticum

The maximum number of major nucleoli (macronucleoli) per nucleus of hexaploid, tetraploid and diploid wheat, Aegilops speltoides and Ae. squarrosa corresponded to the number of satellited chromosomes of each species. Smaller nucleoli (micronucleoli) were rare or absent in all of these species except the hexaploid, in which they were predominantly organized on chromosome arm 5D^s. — Fewer than the maximum number of macronucleoli in a mitotic interphase nucleus resulted from fusion of developing nucleoli. Enforced proximity of nucleolus-organizing regions resulted in more frequent fusion of nucleoli. — Analyses of related interphase nuclei showed that nucleoli, and hence probably chromosomes, undergo limited movement during mitotic interphase. These observations also indicate that specific chromosomes do not occupy specific sites in the interphase nucleus.     

Antarctica on foot: the energy expended to walk,ski and man-haul

Polar exploration often involves travelling on foot and thus is physically intensive, with long-term excursions typically resulting in weight loss. Few studies have investigated the energy expended under such circumstances. Here, we present a range of prediction equations for estimating metabolic rate from heart rate or accelerometry data for specific activities including skiing and man-hauling which can be applied to either short- or long-term excursions. We also use some of these equations to estimate the energy expended undertaking various activities by a team of explorers while attempting to traverse the Antarctic continent during the austral winter of 2013 (as part of the White Mars Project during The Coldest Journey). Calibration equations based on either accelerometry data (from which overall dynamic body acceleration, ODBA, is derived) or heart rate showed good relationships with rate of oxygen consumption, particularly when person height was included. Periods of skiing and man-hauling on The Coldest Journey were estimated to be more energetically demanding (30.0 and 31.1 kJ min^?1, respectively) than walking (24.9 kJ min^?1), or other outdoor work (21.9 kJ min^?1). Estimates of energy expenditure during The Coldest Journey were similar to measures obtained in previous, comparative scenarios. We hope that future expeditions to Antarctica will use these prediction equations to further our understanding of the energy costs of exploring Antarctica and the nutritional requirements needed to guard against emaciation.     

Molecular mechanism of angelman syndrome in two large families involves an imprinting mutation.

Patients with Angelman syndrome (AS) and Prader-Willi syndrome with mutations in the imprinting process have biparental inheritance but uniparental DNA methylation and gene expression throughout band 15q11-q13. In several of these patients, microdeletions upstream of the SNRPN gene have been identified, defining an imprinting center (IC) that has been hypothesized to control the imprint switch process in the female and male germlines. We have now identified two large families (AS-O and AS-F) segregating an AS imprinting mutation, including one family originally described in the first genetic linkage of AS to 15q11-q13. This demonstrates that this original linkage is for the 15q11-q13 IC. Affected patients in the AS families have either a 5.5- or a 15-kb microdeletion, one of which narrowed the shortest region of deletion overlap to 1.15 kb in all eight cases. This small region defines a component of the IC involved in AS (ie., the paternal-to-maternal switch element). The presence of an inherited imprinting mutation in multiple unaffected members of these two families, who are at risk for transmitting the mutation to affected children or children of their daughters, raises important genetic counseling issues.     

Psychogenetically selected (Roman high- and low-avoidance) rats differ in 24-hour sleep organization.

A comparison of sleep organization in Roman high-(RHA/Verh) and low-(RLA/Verh) avoidance rats, which differ in the way they respond to environmental stimuli and in several neuroendocrine and neurochemical parameters, was carried out. EEG-sleep recordings were obtained from adult males over 12:12 light-dark periods to determine how these two psychogenetically selected rat lines might also differ in their sleep-wake cycle. There was no significant difference in total sleep time between the two lines. However, the (hypoemotional) RHA/Verh rats showed an overall increase (percentage of total sleep) in paradoxical sleep (PS) duration, with a concomitant decrease in slow-wave sleep (SWS). During the dark phase, RHA/Verh rats showed a shorter PS latency and a larger number of PS episodes. Hourly sleep scoring also revealed a more discontinuous pattern (total sleep and PS vs. SWS) during the dark phase in RHA/Verh rats. In relation to recognized neurochemical and neuroendocrine differences between them, these rat lines may prove useful in investigations of the neurobiological mechanisms underlying sleep regulation.