Nitric oxide coordinates metabolism, growth and development via the Nuclear Receptor E75|
Nitric oxide coordinates metabolism, growth and development via the Nuclear Receptor E75
Lucía Cáceres, Aleksandar S. Necakov, Carol Schwartz, Sandra Kimber, Ian J. H. Roberts and Henry M. Krause
In this paper, Caceres et al. reveal that the E75/Rev-erb family of nuclear receptors mediates nitric oxide (NO)signaling in the nucleus, and its regulation of development and metabolism. The authors show that in the main neuroendocrine gland of Drosophila - the prothoracic gland - NO produced by NO synthase (NOS) blocks the repressive interaction between the E75 nuclear receptor, and it heterodimer partner, DHR3, which, in turn, activates expression of the metamorphosis hormone, ecdysone. Overexpression and underexpression experiments in the prothoracic gland demonstrated the crucial role of NO and E75 nuclear receptor signaling in metamorphosis and metabolism: overexpression lead to massive obesity caused by excessive larval feeding and fat deposition, while disruption lead to a 100-fold decrease in larval size (compared to overexpression counterparts).
The relative ratio of condensin I to II determines chromosome shapes
Keishi Shintomi and Tatsuya Hirano
129 years after mitotic chromosomes were first described by Walther Flemming, Shintomi and Hirano finally reveal what determines their shape. Metaphase chromosomes shape varies – both during the development of an organism, as well as between different organisms. Shintomi and Hirano precisely manipulated the relative ratios of condensin I and II proteins in Xenpous egg cell-free extracts to demonstrate that these ratios regulate the shape of mitotic chromosomes. They also provided evidence that the cohesion protein helps juxtapose sister chromatid arms by collaborating with condensin I and antagonizing condensin II. Ultimately, the study shows that “chromosome shaping is achieved by an exquisite balance among condensin I (lateral compaction),condensin II (axial shortening) and cohesin (sister chromatid cohesion).”
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