Figure 4.

Decreased telomerase activity and normal expression of telomere-binding proteins in the absence of Dicer. (a) Expression levels of the indicated telomerase components in wild-type and Dicer1-null ES cells using Agilent 4×44K mouse 60-mer oligonucleotide microarrays. Data are mean values from two experiments using cells derived from two independent Dicer1-null cultures (27G5 and 27H10). Statistical significance using the Student’s t-test is also indicated. Note the absence of significant differences between genotypes. (b) Expression levels of the indicated telomere-binding proteins determined as in part a. Statistical significance using the Student’s t-test is indicated. (c) Representative western blots showing the abundance of telomere repeat binding factors 1 and 2 (TRF1 and TRF2) in the indicated genotypes. Quantification is shown below. Statistical significance is indicated. NS, not significant. (d) Representative images of telomerase telomere repeat amplification protocol (TRAP) activity in the indicated genotypes are shown on the left. (+), treated with RNase; (–), not treated with RNase. Quantification of telomerase TRAP activity levels in the indicated genotypes is shown on the right. a.u., arbitrary units.