The human exosome: an autoantigenic complex of exoribonucleases in myositis and scleroderma

The anti-PM/Scl autoantibodies are known to characterize a subset of autoimmune patients with myositis, scleroderma (Scl), and the PM/Scl overlap syndrome. The major autoantigens that are recognized by anti-PM/Scl autoantibodies are designated PM/Scl-100 and PM/Scl-75. These autoantigens have been reported to associate into a large complex consisting of 11 to 16 proteins and to play a role in ribosome synthesis. Recently, it was discovered that the PM/Scl complex is the human counterpart of the yeast (Saccharomyces cerevisiae) exosome, which is an RNA-processing complex consisting of 11 3' → 5' exoribonucleases. To date, 10 human exosome components have been identified, although only some of these were studied in more detail. In this review, we discuss some recent advances in the characterization of the PM/Scl complex.     

Electrochemical characterization of immobilized NAD+

Nicotinamide adenine dinucleotide (NAD⁺) has been covalently attached to alginic acid using carbodiimide coupling, thereby producing a macromolecular adduct of NAD, which can be rendered either soluble or insoluble by adjustment of pH. It was found that this NAD⁺ · alginic acid complex was enzymatically active, and also that the oxidized form could be electrochemically reduced without loss in enzymatic activity. This NAD⁺ adduct has now also been polarographically characterized as to its two-step reduction waves, which are slightly shifted toward more cathodic potential as compared to free NAD⁺. When controlled electrolysis was conducted to reduce the bound NAD⁺ at the cathode, the NADH so formed by electrochemical action was found to be again oxidizable either enzymatically or electrochemically without loss in co-enzymic function. The NADH adduct produced by electrochemical reduction of the NAD⁺ adduct has also been characterized by voltammetry.