No abstract

Our results suggest that SMP30 protects mice lungs from oxidative stress associated with aging and smoking. The SMP30Y/- mice could be useful animal models for investigating age-related lung diseases, including cigarette smoke-induced pulmonary emphysema.

The pre-mRNA splicing reaction of eukaryotic cells has to be carried out extremely accurately, as failure to recognize the splice sites correctly causes serious disease. The small subunit of the U2AF heterodimer is essential for the determination of 3 ′ splice sites in pre-mRNA splicing, and several single-residue mutations of the U2AF small subunit cause severe disorders such as myelodysplastic syndromes. However, the mechanism of RNA recognition is poorly understood. Here we solved the crystal structure of the U2AF small subunit (U2AF23) from fission yeast, consisting of an RNA recognition motif (RRM) domain flanked by two conserved CCCH-type zinc fingers (ZFs). The two ZFs are positioned side by side on the β sheet of the RRM domain. Further mutational analysis revealed that the ZFs bind cooperatively to the target RNA sequence, but the RRM domain acts simply as a scaffold to organize the ZFs and does not itself contact the RNA directly. This completely novel and unexpected mode of RNA-binding mechanism by the U2AF small subunit sheds light on splicing errors caused by mutations of this highly conserved protein.

No abstract

The senescence-accelerated mouse (SAM) is a naturally occurring animal model for accelerated aging after normal development and maturation. SAMP1 strain was reported to show age-related structural and functional changes in lung and to be a murine model of senile lung. We postulated that aging of lung is an important intrinsic process for development of emphysema and even in a short period of tobacco smoke exposure may be able to generate emphysema. At age 12 wk, SAMP1 inhaled air or 1.5% tobacco smoke (total particulate matter 23.9 mg/m3) through the nose for 30 min/day, 5 days/wk, and for 8 wk. The mean linear intercepts (MLI) and destructive index (DI) of lung were significantly increased [air vs. smoke (means+/-SE); MLI, 68.76+/-0.69 vs. 75.34+/-1.70 microm, P<0.05 and DI, 8.61+/-0.38 vs. 16.18+/-1.54%, P<0.05], whereas no significant changes were observed in SAMR1, control mice that show normal aging. In contrast, smoke-induced emphysema was completely prevented by concomitant ingestion of lycopene given as tomato juice [MLI: smoke with/without lycopene (mean+/-SE), 62.87+/-0.8 vs. 66.90+/-1.33 microm, P<0.05]. Smoke exposure increased apoptosis and active caspase-3 of airway and alveolar septal cells and reduced VEGF in lung tissues, but tomato juice ingestion significantly reduced apoptosis and increased tissue VEGF level. We conclude that SAMP1 is a useful model for tobacco smoke-induced emphysema and a valuable tool to explore both pathophysiological mechanisms and the effect of therapeutic intervention on smoke-induced emphysema.