Research Paper Volume 8, Issue 3 pp 484—505

Figure 1. Increased expression of the mitochondrial sirtuin SIRT4 in human fibroblasts undergoing replicative or UVB-induced senescence. (A) Concomitant upregulation of SIRT4 and p21^WAF expression during replicative senescence. Human foreskin fibroblast lines (from n=4 donors; mean ± s.d.) were analysed at increasing passage numbers for SIRT4 and p21^WAF mRNA levels by quantitative real-time polymerase chain reaction (qRT-PCR; suppl. Material & Methods). To evaluate statistical significance, ANOVA (on ranks for SIRT4) SNK were performed (*p<0.05). (B) Primary human dermal fibroblasts (n=4 donors; mean ± s.d.) were subjected to repetitive ultraviolet irradiation (100 J/m² UVB per day) or infrared irradiation (360 J/m² UVB per day) for a total of five days. Cells were harvested 24 and 72 h following the last irradiation and SIRT4 mRNA levels were determined by qRT-PCR. To evaluate statistical significance ANOVA on ranks (SNK) were performed (*p<0.05).