Cellular senescence takes days to weeks to become fully established, with autocrine biochemical loops involving reactive oxygen species (ROS), IL-6, transforming growth factor-β, and other signals eventually resulting in focal accumulation of heterochromatin (Passos et al. 2010; Kuilman et al., 2008; Kuilman & Peeper, 2009; Passos et al., 2009).
Biochemists have long known that these cycles are the result of various biochemical feedback loops in which the transcription of genes is boosted and damped.
Our results suggest that the persistent polarization underlying many cellular and developmental processes could arise through a simple biophysical process, without any additional biochemical feedback loops.
In most mitotic cells, complex biochemical regulatory loops ensure that its two major activators function sequentially; Cdc20/Fizzy drives the metaphase-to-anaphase transition, while the tumor suppressor Cdh1 not only drives mitotic exit but also represses subsequent cell cycle entry and promotes somatic cell differentiation (reviewed in Peters 2006; Thornton and Toczyski 2006; Wasch et al. 2010).
The biochemical relevance of loop 301−304 is unclear because it is far away from both the putrescine binding site and the active site.
Various methods have been used to study the DNA : NM attachment points (Mirkovitch et al. 1984) including imaging by FISH and Maximum Fluorescence Halo Radius (MFHR) (Fig. 1), and biochemical (digestion of loop DNA with restriction enzymes, DNase I or topoisomerase II).
To preserve strong synapses despite these processes, some proposed mechanisms hypothesize biochemical positive feedback loops.
Previous models (see Introduction) have postulated that bistability in synaptic strength could be generated by biochemical positive feedback loops involving kinase activation or mRNA translation.
GVDM carried out the mice breeding, treatments, biochemical analysis, PV-loop experiments and infarct size determination, data and statistical analysis, and drafted the manuscript.
We previously posed the possibility that the PKMζ network is bistable [ 13], since biochemical positive feedback loops often offer bistability [ 14, 15].
