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Cellular senescence correlates with changes in the transcriptome. To obtain a complete view on senescence-associated transcription networks and pathways, we assessed by deep RNA sequencing the transcriptomes of five of the most commonly used laboratory strains of human fibroblasts during their transition into senescence. In a number of cases, we verified the RNA-seq data by real-time PCR. By determining cellular protein levels we observed that the age-related expression of most but not all genes is regulated at the transcriptional level. We found that 78% of the age-affected differentially expressed genes were commonly regulated in the same direction (either up- or down-regulated) in all five fibroblast strains, indicating a strong conservation of age-associated changes in the transcriptome. KEGG pathway analyses confirmed up-regulation of the senescence-associated secretory phenotype and down-regulation of DNA synthesis/repair and most cell cycle pathways common in all five cell strains. Newly identified senescence-induced pathways include up-regulation of endocytotic/phagocytic pathways and down-regulation of the mRNA metabolism and the mRNA splicing pathways. Our results provide an unprecedented comprehensive and deep view into the individual and common transcriptome and pathway changes during the transition into of senescence of five human fibroblast cell strains.

The paper describes the Rosetta Lander named Philae and introduces its complement of scientific instruments. Philae was launched aboard the European Space Agency Rosetta spacecraft on 02 March 2004 and is expected to land and operate on the nucleus of 67P/Churyumov-Gerasimenko at a distance of about 3 AU from the Sun. Its overall mass is ∼98 kg (plus the support systems remaining on the Orbiter), including its scientific payload of ∼27 kg. It will operate autonomously, using the Rosetta Orbiter as a communication relay to Earth. The scientific goals of its experiments focus on elemental, isotopic, molecular and mineralogical composition of the cometary material, the characterization of physical properties of the surface and subsurface material, the large-scale structure and the magnetic and plasma environment of the nucleus. In particular, surface and sub-surface samples will be acquired and sequentially analyzed by a suite of instruments. Measurements will be performed primarily during descent and along the first five days following touch-down. Philae is designed to also operate on a long time-scale, to monitor the evolution of the nucleus properties. Philae is a very integrated project at system, science and management levels, provided by an international consortium. The Philae experiments have the potential of providing unique scientific outcomes, complementing by in situ ground truth the Rosetta Orbiter investigations.

Promyelocytic leukemia (PML) nuclear bodies constitute one class of intranuclear domains that may be directly involved in the expression of specific genes. Here we have analyzed the spatial relationship between PML bodies and sites of transcriptional activity by indirect immunofluorescence and confocal microscopy during the cell cycle. In unsynchronized mammalian cells approx 30% of PML bodies are spatially associated with transcription sites. These sites contain hyperphosphorylated RNA polymerase II, indicating active mRNA transcription tightly associated with the PML body. In G1 phase of the cell cycle more than 70% of PML bodies contain active transcription foci. A similarly high degree of colocalization (approx 80%) between PML bodies and sites of active transcription was also observed when the cells were exposed to interferon-γ. We also show that the hypophosphorylated form of RNA polymerase II and the transcriptional coactivator CBP colocalize within PML bodies predominantly in G1. Our observations suggest that PML bodies may be recruited to nuclear sites of induced or up-regulated mRNA transcription where it may serve as a scaffold for factors involved in expression of specific genes.