Effects of miR-122 abundance on Insig1 mRNA isoform abundances. (A) (Left panel) Northern blot for mature miR-122. miR-122 is expressed mainly as three isofroms of 21, 22, and 23 nt in length. Cells were depleted of sterols overnight and re-fed with sterols and mevalonate for 2 and 4 h, and mature (middle panel) and precursor (right panel) miR-122 abundance measured by Northern blot. The differences of abundance of the mature microRNAs after sterol add-back were statistically not significant (all P-values were larger than 0.57). The differences in abundance between pri-miR-122 from 0 to 2, and from 0 to 4 h after sterol add-back were significant, with P-values of 0.0567 and 0.097, respectively. (B–D) Cells were transfected with antisense locked nucleic acids (LNA) against miR-122, miR-106b/miR-93, or miR-25/miR-92 and depleted of sterols overnight. At time zero, cells were re-fed with sterols and mevalonate and total RNA harvested at the indicated time points. Insig1 mRNA isoforms were visualized by Northern blot analysis and quantitated using normalization to actin mRNA. RNA abundances from cells transfected with antisense (as) miR-106b/93 LNA at time zero were set to one. The data are representative of at least three independent replicates. Error bars represent standard error of the mean.
