measuring-interpreting-oxygen-consumption-rates-whole-fly-head

Measuring and Interpreting Oxygen Consumption Rates in Whole Fly Head Segments

Regulated metabolic activity is essential for the normal functioning of living cells. Indeed, altered metabolic activity is causally linked with the ...

Ludwig-Maximilians University of Munich

The structure of chromatin is critical for many aspects of cellular physiology and is considered to be the primary medium to store epigenetic information. It is defined by the histone molecules that constitute the nucleosome, the positioning of the nucleosomes along the DNA and the non-histone proteins that associate with it. These factors help to establish and maintain a largely DNA sequence-independent but surprisingly stable structure. Chromatin is extensively disassembled and reassembled during DNA replication, repair, recombination or transcription in order to allow the necessary factors to gain access to their substrate. Despite such constant interference with chromatin structure, the epigenetic information is generally well maintained. Surprisingly, the mechanisms that coordinate chromatin assembly and ensure proper assembly are not particularly well understood. Here, we use label free quantitative mass spectrometry to describe the kinetics of in vitro assembled chromatin supported by an embryo extract prepared from preblastoderm Drosophila melanogaster embryos. The use of a data independent acquisition method for proteome wide quantitation allows a time resolved comparison of in vitro chromatin assembly. A comparison of our in vitro data with proteomic studies of replicative chromatin assembly in vivo reveals an extensive overlap showing that the in vitro system can be used for investigating the kinetics of chromatin assembly in a proteome-wide manner. 

A Quantitative Proteomic Analysis of In Vitro Assembled Chromatin.

Loss of cellular homeostasis during aging results in altered tissue functions and leads to a general decline in fitness and, ultimately, death. As animals age, the control of gene expression, which is orchestrated by multiple epigenetic factors, degenerates. In parallel, metabolic activity and mitochondrial protein acetylation levels also change. These two hallmarks of aging are effectively linked through the accumulating evidence that histone acetylation patterns are susceptible to alterations in key metabolites such as acetyl-CoA and NAD(+), allowing chromatin to function as a sensor of cellular metabolism. In this review we discuss experimental data supporting these connections and provide a context for the possible medical and physiological relevance.

The Metabolic Impact on Histone Acetylation and Transcription in Ageing.

DNA replication and subsequent deposition of nucleosomes is critical for the maintenance of the genome and epigenetic inheritance. Experiments using human tissue culture cells harvested at defined stages of the cell cycle can help to elucidate the mechanism of histone deposition and chromatin assembly in detail. Here, we describe a pulsed-SILAC approach to distinguish newly synthesized and deposited histones during S-phase of the cell cycle from parental "old" histones incorporated in previous replications and to decipher posttranslational histone modifications (PTMs).

Axel Imhof

Munich Center of Integrated Protein Science and Biomedical Center

Ludwig-Maximilians University of Munich

Measuring and Interpreting Oxygen Consumption Rates in Whole Fly Head Segments