Upper Palaeolithic infant burials

Decorations on the bodies of newborns indicate that they were probably important in their community. Several adult graves from the Stone Age (Upper Palaeolithic period) have been found but child burials seem to be rare, which has prompted discussion about whether this apparently different treatment of infants could be significant. Here we describe two recently discovered infant burials from this period at Krems-Wachtberg in Lower Austria, in which the bodies were covered with red ochre and decorated with ornaments and were therefore probably ritually buried. These findings indicate that even newborns were considered to be full members of these hunter-gatherer communities about 27,000 years ago.     

Real-time observation of trigger factor function on translating ribosomes

The contribution of co-translational chaperone functions to protein folding is poorly understood. Ribosome-associated trigger factor (TF) is the first molecular chaperone encountered by nascent polypeptides in bacteria. Here we show, using fluorescence spectroscopy to monitor TF function and structural rearrangements in real time, that TF interacts with ribosomes and translating polypeptides in a dynamic reaction cycle. Ribosome binding stabilizes TF in an open, activated conformation. Activated TF departs from the ribosome after a mean residence time of approximately 10 s, but may remain associated with the elongating nascent chain for up to 35 s, allowing entry of a new TF molecule at the ribosome docking site. The duration of nascent-chain interaction correlates with the occurrence of hydrophobic motifs in translating polypeptides, reflecting a high aggregation propensity. These findings can explain how TF prevents misfolding events during translation and may provide a paradigm for the regulation of nucleotide-independent chaperones.     

Control of spontaneous and damage-induced mutagenesis by SUMO and ubiquitin conjugation

Protein modification by ubiquitin is emerging as a signal for various biological processes in eukaryotes, including regulated proteolysis, but also for non-degradative functions such as protein localization, DNA repair and regulation of chromatin structure. A small ubiquitin-related modifier (SUMO) uses a similar conjugation system that sometimes counteracts the effects of ubiquitination. Ubiquitin and SUMO compete for modification of proliferating cell nuclear antigen (PCNA), an essential processivity factor for DNA replication and repair. Whereas multi-ubiquitination is mediated by components of the RAD6 pathway and promotes error-free repair, SUMO modification is associated with replication. Here we show that RAD6-mediated mono-ubiquitination of PCNA activates translesion DNA synthesis by the damage-tolerant polymerases eta and zeta in yeast. Moreover, polymerase zeta is differentially affected by mono-ubiquitin and SUMO modification of PCNA. Whereas ubiquitination is required for damage-induced mutagenesis, both SUMO and mono-ubiquitin contribute to spontaneous mutagenesis in the absence of DNA damage. Our findings assign a function to SUMO during S phase and demonstrate how ubiquitin and SUMO, by regulating the accuracy of replication and repair, contribute to overall genomic stability.     

Joint insolation and ice sheet/CO2 forcing on northern China precipitation during Pliocene warmth

East Asian summer monsoon (EASM) precipitation affects the lives of billions of people and impacts the stability of fragile desert ecosystems in central Asia [1...