Priority Research Paper Volume 1, Issue 7 pp 608—621

Figure 4. The up-regulation of ISG1 5 expression in cells with short telomeres does not depend on interferon beta1 (INFB1). (A) Q-PCR analysis of mRNA levels of INFB1 in human fibroblasts with different telomere length (BJ-18 to BJ-83). Results from at least three separate experiments are shown as means ± SEM. GAPDH was used as an internal normalization control. All values were then normalized to the level (=100%) of mRNA in young cells (PD18) with long telomeres. Results show an increase of INFB1 expression with telomere shortening. (B) Stable knock down of INFB1 by shRNA in BJ cells with short telomeres did not reduce the expression of ISG15. mRNA levels of ISG15 and INFB1 were quantified by q-PCR. (C) Western blot showing that blocking antibodies to both IFN α and β reduced the levels of both free and conjugated ISG15 in young BJ fibroblasts, but failed to reduce expression in old cells with short telomeres. Young (BJ-18) and old (BJ-76) cells were treated with neutralizing antibodies against INFA and INFB1.