Effects of NOP58 and CBF5 knockdown. (a) Effects of NOP58 and CBF5 silencing on novel snoRNAs and schematic representation of the clusters encoding the snoRNAs. RNA was prepared from cells carrying either NOP58 or CBF5 silencing constructs before induction with Tetracycline (-), and 3 days after addition of tetracycline (+). The RNA was analyzed by primer extension and separated on a 6% denaturing polyacrylamide gel. The level of U6 snRNA was used to examine the amount of RNA the samples. The same RNA was used for the different primer extension assays. The positions of the snoRNAs in the genome are given on the left. The sizes of the snoRNAs and the intergenic regions (in nucleotides) are given below each diagram. The number of times the gene cluster (delineated by parentheses) is repeated is given on the right. The inset shows the controls: TB11Cs2C2, a known C/D molecule, and SLA1, a known H/ACA molecule, for which a significant reduction in expression following silencing can be seen, and U6 snRNA, a non-snoRNA molecule which is not affected. Novel C/D and H/ACA molecules were named as such based on the nomenclature of Liang et al. 2005 . (b) Putative interaction domains for the C/D molecules TB2Cs1C1, TB10Cs2''C1, and TB10Cs2"C3. For TB10Cs2''C3, two putative targets are listed.