A review of non-cancer effects, especially circulatory and ocular diseases

There is a well-established association between high doses (>5 Gy) of ionizing radiation exposure and damage to the heart and coronary arteries, although only recently have studies with high-quality individual dosimetry been conducted that would enable quantification of this risk adjusting for concomitant chemotherapy. The association between lower dose exposures and late occurring circulatory disease has only recently begun to emerge in the Japanese atomic bomb survivors and in various occupationally exposed cohorts and is still controversial. Excess relative risks per unit dose in moderate- and low-dose epidemiological studies are somewhat variable, possibly a result of confounding and effect modification by well-known (but unobserved) risk factors. Radiation doses of 1 Gy or more are associated with increased risk of posterior subcapsular cataract. Accumulating evidence from the Japanese atomic bomb survivors, Chernobyl liquidators, US astronauts, and various other exposed groups suggests that cortical cataracts may also be associated with ionizing radiation, although there is little evidence that nuclear cataracts are radiogenic. The dose–response appears to be linear, although modest thresholds (of no more than about 0.6 Gy) cannot be ruled out. A variety of other non-malignant effects have been observed after moderate/low-dose exposure in various groups, in particular respiratory and digestive disease and central nervous system (and in particular neuro-cognitive) damage. However, because these are generally only observed in isolated groups, or because the evidence is excessively heterogeneous, these associations must be treated with caution.     

In silico investigation of novel biological pathways: The role of CD200 in regulation of T cell priming in experimental autoimmune encephalomyelitis

The use of simulation to investigate biological domains will inevitably lead to the need to extend existing simulations as new areas of these domains become more fully understood. Such simulation extensions can entail the incorporation of additional cell types, molecules or molecular pathways, all of which can exert a profound influence on the simulation behaviour. Where the biological domain is not well characterised, a structured development methodology must be employed to ensure that the extended simulation is well aligned with its predecessor. We develop and discuss such a methodology, relying on iterative simulation development and sensitivity analysis. The utility of this methodology is demonstrated using a case study simulation of experimental autoimmune encephalomyelitis (EAE), a murine T cell-mediated autoimmune disease model of multiple sclerosis, where it is used to investigate the activity of an additional regulatory pathway. We discuss how application of this methodology guards against creating inappropriate simulation representations of the biology when investigating poorly characterised biological mechanisms.     

Structural insights into the targeting of mRNA GU-rich elements by the three RRMs of CELF1

The CUG-BP, Elav-like family (CELF) of RNA-binding proteins control gene expression at a number of different levels by regulating pre-mRNA splicing, deadenylation and mRNA stability. We present structural insights into the binding selectivity of CELF member 1 (CELF1) for GU-rich mRNA target sequences of the general form 5′-UGUN_xUGUN_yUGU and identify a high affinity interaction (K_d ∼ 100 nM for x = 2 and y = 4) with simultaneous binding of all three RNA recognition motifs within a single 15-nt binding element. RNA substrates spin-labelled at either the 3′ or 5′ terminus result in differential nuclear magnetic resonance paramagnetic relaxation enhancement effects, which are consistent with a non-sequential 2-1-3 arrangement of the three RNA recognition motifs on UGU sites in a 5′ to 3′ orientation along the RNA target. We further demonstrate that CELF1 binds to dispersed single-stranded UGU sites at the base of an RNA hairpin providing a structural rationale for recognition of CUG expansion repeats and splice site junctions in the regulation of alternative splicing.     

Disulfide reduction abolishes tissue factor cofactor function

Background

Tissue factor (TF), an in vivo initiator of blood coagulation, is a transmembrane protein and has two disulfides in the extracellular domain. The integrity of one cysteine pair, Cys186–Cys209, has been hypothesized to be essential for an allosteric “decryption” phenomenon, presumably regulating TF procoagulant function, which has been the subject of a lengthy debate. The conclusions of published studies on this subject are based on indirect evidences obtained by the use of reagents with potentially oxidizing/reducing properties.

Methods

The status of disulfides in recombinant TF_1–263 and natural placental TF in their non-reduced native and reduced forms was determined by mass-spectrometry. Functional assays were performed to assess TF cofactor function.

Results

In native proteins, all four cysteines of the extracellular domain of TF are oxidized. Reduced TF retains factor VIIa binding capacity but completely loses the cofactor function.

Conclusion

The reduction of TF disulfides (with or without alkylation) eliminates TF regulation of factor VIIa catalytic function in both membrane dependent FX activation and membrane independent synthetic substrate hydrolysis.

General significance

Results of this study advance our knowledge on TF structure/function relationships.