Knock-down of endogenous Maf1 increases the levels of unstable tRNA precursors.

<p>A) Knock-down of endogenous Maf1 in untransformed cells. Exponentially growing IMR-90Tert cells were either left untransfected, or transfected with either siRNAs #2 or #3 against MAF1, or with a control siRNA, as indicated on top of the panel. RNA was then isolated from untransfected or transfected cells and 2 µg of total RNA used for random-primed reverse transcription. The resulting cDNA was analyzed by real-time quantitative PCR (qPCR) with primers corresponding to either Maf1 (black bars), tRNA^Tyr precursor (yellow bars), or GAPDH as a control (blue bars). B) and C) Knock-down of endogenous Maf1 in transformed cells. In B, the levels of either α-tubulin as a loading control (upper panel) or Maf1 (lower panel) were analyzed by western-blot in extracts from either untransfected 293 cells (lane 1) or 293 cells transfected with the siRNAs indicated above the lanes (lanes 2–5). In C, 293 cells were either left untransfected (lane 1) or transfected with the siRNAs indicated above the lanes. Cellular RNA was then collected and analyzed by northern blot with a probe detecting U2 snRNA precursors as a control (upper panel), or intron-containing tRNA^Leu (middle panel) and tRNA^Tyr (bottom panel) precursors.