Loss of SLIRP compromises the stability of mitochondrial mRNAs and LRPPRC.

<p>(A) Immunoblot of SLIRP and LRPPRC protein levels in heart, liver and kidney mitochondria from 12-week old wild-type (<i>Slirp</i>^+/+), <i>Slirp</i> homozygous knockout (KO, <i>Slirp</i>^-/-) and <i>Lrpprc</i> heterozygous KO (<i>Lrpprc</i>^+/-) mice. VDAC was used as a loading control. (B) Representative confocal microscopy images of <i>Slirp</i>^+/+ (left) and <i>Slirp</i>^-/- (right) MEFs, stained for LRPPRC and TOM20 as a mitochondrial marker. Magnifications of the dashed boxed areas show merged channels of LRPPRC and TOM20 (bottom, left) and single channels of LRPPRC (bottom, right). Scale bars presented, 10 μm. (C) <i>In organello de novo</i> transcription assays performed on heart and liver mitochondria isolated from 12-week old <i>Slirp</i>^+/+ and <i>Slirp</i>^-/- mice. VDAC was used as a loading control. (D) Mitochondrial tRNA steady-state levels assessed by northern blotting in hearts of 12-week old <i>Slirp</i>^+/+<i>and Slirp</i>^-/- mice. (E) Mitochondrial transcript steady-state levels assessed by qRT-PCR in hearts from 12-week old <i>Slirp</i>^+/+ (white bars) and <i>Slirp</i>^-/- (black bars) mice, as well as in hearts from 12-week old <i>Lrpprc</i> control (<i>Lrpprc</i> p/p, light grey bars) and conditional KO (<i>Lrpprc</i> p/p, cre, dark grey bars), n = 5. Error bars represent SEM. * p value < 0.05. ** p value < 0.01. *** p value < 0.001. (F) Measurement of mitochondrial transcript poly(A) tail length from heart mitochondria of <i>Slirp</i>^+/+ (white bars), <i>Slirp</i>^-/- (black bars), <i>Lrpprc</i>^+/- (yellow bars) and <i>Lrpprc</i> p/p, cre (grey bars) mice. Error bars represent SEM. n.s. means not significant. * p value < 0.05.