Effects of aging and dietary restriction on ubiquitination, sumoylation, and the proteasome in the spleen.

In the present study, we demonstrate for the first time that aging increases the levels of ubiquitinated protein in the spleen, and that dietary restriction (DR) significantly reduces these age-related increases in ubiquitinated protein. Sumoylated protein, proteasome subunits, and a protein essential for proteasome biogenesis (POMP1) were also increased with age in the spleen but were not significantly affected by DR. Chymotrypsin-like proteasome activity was elevated in the aged spleen, and was not significantly altered by DR. Together, these data demonstrate for the first time the multiple effects of aging and DR on ubiquitination, sumoylation, and the proteasome in the spleen.