Novel components of human mitotic chromosomes identified by proteomic analysis of the chromosome scaffold fraction

Chromosomal nonhistone proteins have important roles in mitotic chromosome formation and dynamics. In order to identify novel abundant proteins with a potential involvement in these processes, we initiated a proteomic screen of the chromosome scaffold fraction. This screen identified 79 proteins, 30 of which had not previously been described as components of mitotic chromosomes. Furthermore, half of these proteins had no documented function. We analyzed the cell-cycle dependent distribution of three uncharacterized proteins by expressing them as green fluorescent protein (GFP) fusions and showed that they associate with mitotic chromosomes in vivo. One of the proteins, nuclear protein p30, is a novel component of the inner centromere. Over-expression experiments indicated that p30 may have an active role in the formation of centromeric heterochromatin.     

Saisonaler Verlauf der Gesangsaktivit?t der Singdrossel(Turdus philomelos), mit Anmerkungen zum nachbrutzeitlichen Gesangsschub

Zusammenfassung Der Zürichbergwald ist eine 350 ha große, bewaldete Kuppe auf 480–680 m ü.M. am Rande der Stadt Zürich. Hier untersuchten wir von 1989 bis 1995 die jahreszeitliche Gesangsaktivität der Singdrossel mit zwei verschiedenen Ansätzen. 1989 und 1991–1995 zählte JH an 123 Tagen auf zwei festgelegten Strecken von 6,1 und 7,1 km die Sänger jeweils in der Stunde der abendlichen Dämmerung. Im gleichen Gebiet zählte RS 1990 an 46 Tagen auf einer 6,7 km langen Strecke am Morgen in der Stunde nach Sonnenaufgang. Ebenfalls 1990 sammelte RS Daten zur Brutbiologie.Die Gesangsaktivität definierten wir mit der Anzahl singender Männchen pro km. Im Jahresverlauf zeigen die Kurven der Morgen- und der Abendaktivität keinen Unterschied. Die Kurve ist deutlich dreiphasig: Ein erster Gesangsschub vom Eintreffen der Vögel bis zum 5. April, danach eine gesangsarme Zwischenzeit bis zum 15. Mai, gefolgt von einem zweiten Gesangsschub, welcher bis zum 5. Juli dauern kann. Allenfalls ist der erste Gesangsschub (stark zeitverschoben) mit dem Beginn der Erstbruten korreliert; die von vielen Singvögel bekannte, markante Gesangsaktivität unmittelbar vor der Eiablage gibt es nicht. Der zweite Gesangsschub ist in der Stärke mit dem ersten vergleichbar. Allerdings liegt er eindeutig am Ende der Brutzeit und kann nicht mit einem Brutparameter (Partnerfindung, Paarbindung, Balz, Brut-Stimulation) in Zusammenhang stehen. Die Funktion dieser nachbrutzeitlichen Gesangsaktivität scheint zukunftsbezogen zu sein. In Frage kommt gehäuftes Singen der Väter vor den Jungen zum Erlernen des Gesangs und des Dialekts, oder/und eine Revier-Voranzeige für die nänchste Brutsaison durch die als philopatrisch bekannten Männchen.

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Annual variation in singing activity of the Song Thrush(Turdus philomelos), with comments on high postbreeding song output

Summary This study was carried out at the Zürichbergwald, a forest east of Zurich (47°20N/08°30E). The study site is a wooded hill of 350 ha between 480 to 680 m asl, characterised by a BeechFagus silvatica forest with patches of SprucePicea abies on 25 % of its surface. The Zürichbergwald is a popular recreational area with moderate forestry exploitation. We did not differentiate acoustic registration from singing activity, and we considered the number of singing males per km to be a measure for singing activity. Two different approaches were applied: in 6 breeding seasons (1989 and 1991 to 1995) JH counted birds at sunset on a 6.1 or 7.1 km circuit (n=123). In 1990, the same was done by RS at dawn each morning on a zigzag track of 6.7 km (n=46). Also in 1990, RS sampled data on the breeding biology of the species.The annual cycle of morning and evening song activity was significantly correlated (Spearman's rank-test; p<0.001 comparing pentads, p=0.025 comparing half of months). Morning and evening revealed the same pattern: there was a first large peak of singing activity early in the year (earliest onset of singing 19 February 1989; latest 8 March 1993) until 5 April (phase I). A period of low song activity followed from 6 April to 15 May (phase II). The period from 16 May to (circa) 5 July was characterized by a second large peak (phase III). Each of the corresponding phases was comparable between morning and evening (Wilcoxon matching pairs; p>0.05). The analysis of evening data reveals that phase II differed from I and from III (p=0.05), but the last two did not differ significantly (Wilcoxon matching pairs; p>0.05).The day with the highest song activity fell in phase I twice (maximum 6.1 singing males/km, 2 April 1995) and 5 times in phase III (maximum 6.9 singing males/km, 23 May 1994).The date females first laid was determined for 53 out of 68 nests. The first brood started 25 March, the last 25 June 1990. Only 3 broods were initiated later than 5 June.The first peak of singing activity could be correlated with the (delayed) onset of breeding, but the second started at the end of the breeding season and persisted too long to be correlated with any breeding activity such as female attraction or stimulation, mate-guarding, etc. We postulate the high post-breeding song output to have several possible functions: Song instruction by father to offspring, or territory announcement for the next season.

     

XRCC1 is required for DNA single-strand break repair in human cells

The X-ray repair cross complementing 1 (XRCC1) protein is required for viability and efficient repair of DNA single-strand breaks (SSBs) in rodents. XRCC1-deficient mouse or hamster cells are hypersensitive to DNA damaging agents generating SSBs and display genetic instability after such DNA damage. The presence of certain polymorphisms in the human XRCC1 gene has been associated with altered cancer risk, but the role of XRCC1 in SSB repair (SSBR) in human cells is poorly defined. To elucidate this role, we used RNA interference to modulate XRCC1 protein levels in human cell lines. A reduction in XRCC1 protein levels resulted in decreased SSBR capacity as measured by the comet assay and intracellular NAD(P)H levels, hypersensitivity to the cell killing effects of the DNA damaging agents methyl methanesulfonate (MMS), hydrogen peroxide and ionizing radiation and enhanced formation of micronuclei following exposure to MMS. Lowered XRCC1 protein levels were also associated with a significant delay in S-phase progression after exposure to MMS. These data clearly demonstrate that XRCC1 is required for efficient SSBR and genomic stability in human cells.     

Insect antimicrobial peptides: structures, properties and gene regulation

Antimicrobial peptides (AMPs) are part of the armament that insects have developed to fight off pathogens. Insect AMPs are typically cationic and often made of less than 100 amino acid residues. Although their structures are diverse, most of the AMPs can be assigned to a limited number of families. The most common structures are represented by peptides assuming a alpha-helical conformation in organic solutions or disulfide-stabilized beta-sheets with or without alpha-helical domains present. The diverse activity spectrum of these peptides may indicate different modes of action. Genetic analysis in the Drosophila model evidenced that multiple signal transduction pathways are activating the genes coding AMPs.     

Anti-protozoal and plasmodial FabI enzyme inhibiting metabolites of Scrophularia lepidota roots

The ethanolic root extract of Scrophularia lepidota, an endemic plant of the Turkish flora, has been investigated for its anti-protozoal and inhibitory effect towards plasmodial enoyl-ACP reductase (FabI), a key enzyme of fatty acid biosynthesis in Plasmodium falciparum. Chromatographic separation of the extract yielded 10 iridoids (1-10), two of which are new, and a known phenylethanoid glycoside (11). The structures of the new compounds were determined as 3,4-dihydro-methylcatalpol (8) and 6-O-[4'-O-trans-(3,4-dimethoxycinnamoyl)-alpha-L-rhamnopyranosyl]aucubin (scrolepidoside, 9) by spectroscopic means. The remaining metabolites were characterized as catalpol (1), 6-O-methylcatalpol (2), aucubin (3), 6-O-alpha-L-rhamnopyranosyl-aucubin (sinuatol, 4), 6-O-beta-D-xylopyranosylaucubin (5), ajugol (6), ajugoside (7), an iridoid-related aglycone (10) and angoroside C (11). Nine isolates were active against Leishmania donovani, with the new compound 9 being most potent (IC50 6.1 microg/ml). Except for 4, all pure compounds revealed some trypanocidal potential against Trypanosoma brucei rhodesiense (IC50 values 29.3-73.0 microg/ml). Only compound 10 showed moderate anti-plasmodial (IC50 40.6 microg/ml) and FabI enzyme inhibitory activity (IC50 100 microg/ml). 10 is the second natural product inhibiting the fatty acid biosynthesis of Plasmodium falciparum.     

Migratory sleeplessness in the white-crowned sparrow (Zonotrichia leucophrys gambelii)

Twice a year, normally diurnal songbirds engage in long-distance nocturnal migrations between their wintering and breeding grounds. If and how songbirds sleep during these periods of increased activity has remained a mystery. We used a combination of electrophysiological recording and neurobehavioral testing to characterize seasonal changes in sleep and cognition in captive white-crowned sparrows (Zonotrichia leucophrys gambelii) across nonmigratory and migratory seasons. Compared to sparrows in a nonmigratory state, migratory sparrows spent approximately two-thirds less time sleeping. Despite reducing sleep during migration, accuracy and responding on a repeated-acquisition task remained at a high level in sparrows in a migratory state. This resistance to sleep loss during the prolonged migratory season is in direct contrast to the decline in accuracy and responding observed following as little as one night of experimenter-induced sleep restriction in the same birds during the nonmigratory season. Our results suggest that despite being adversely affected by sleep loss during the nonmigratory season, songbirds exhibit an unprecedented capacity to reduce sleep during migration for long periods of time without associated deficits in cognitive function. Understanding the mechanisms that mediate migratory sleeplessness may provide insights into the etiology of changes in sleep and behavior in seasonal mood disorders, as well as into the functions of sleep itself.     

Angiomotin belongs to a novel protein family with conserved coiled-coil and PDZ binding domains

Angiomotin has previously been identified in a yeast two-hybrid screen by its ability to bind to angiostatin, an inhibitor of novel formation of blood vessels (angiogenesis). Angiomotin mediates the inhibitory effect of angiostatin on endothelial cell migration and tube formation in vitro. Here we report that two human protein sequences, of which one is novel and one has been cloned previously, are similar to angiomotin and are members of a novel protein family, which we propose to call motins. These two genes have been named angiomotin-like 1 (amotl1) and angiomotin-like 2 (amotl2). We have cloned mouse angiomotin and identified amotl1 and amotl2 homologs in mice. The alignment of the amino acid sequences encoded by these six sequences spans 455 residues of which 64% was conserved in all six proteins. Sequence analysis showed that these sequences all share putative coiled-coil domains and PDZ-binding motifs. Sequence information from GenBank indicate that motins can be found in several species including the frog Xenopus laevis, the pufferfish Fugu rubripes and the nematode Caenorhabditis elegans. Further phylogenetic analysis indicates that amotl2 is an evolutionary outgroup in relation to angiomotin and amotl1. Northern blot analysis shows distinct expression patterns for each motin in various mouse tissues.