RNA seq after RNA pol III manipulation by Brf1 and Maf1 knockdown, Maf1 overexpression and ML60218 treatment in ST2 cells before, and during differentiation into osteoblasts

Maf1, a key repressor of RNA polymerase III-mediated transcription, has been shown to promote mesoderm formation in vitro. Here, we show, for the first time, that Maf1 plays a critical role in the regulation of osteoblast differentiation. We also found that, in contrast to MAF1 overexpression, other perturbations that repress RNA pol III transcription, including Brf1 knockdown and the chemical inhibition of RNA pol III by ML-60218, inhibited osteoblast differentiation. RNA-seq was used to determine the basis for these opposing actions on osteoblast differentiation. RNA polymerase III-dependent transcription was manipulated in ST2 stromal cells by Brf1 or Maf1 knockdown, ML-60218 treatment and MAF1 overexpression. The ST2 cells were then tested for their capacity to differentiate into osteoblasts. RNA-seq was performed on day 0, before differentiation and day 4 after differentiation medium was added. The modalities used to perturb RNA pol III transcription resulted in distinct changes gene expression, indicating that this transcription process is highly sensitive and triggers diverse gene expression programs and phenotypic outcomes. Specifically, Maf1 induced genes in ST2 cells known to promote osteoblast differentiation. Furthermore, genes that are induced during osteoblast differentiation displayed codon bias. Overall design: Comparative gene expression profiling analysis of RNA-seq data for ST2 cells before (d0), and during (d4) osteoblast differentiation. cells were manipulated by shBrf1 (=shBr) or SCRB control, shMaf1(=shMA) or SCRM control, pinducer20-MAF1 (=MAF1) or pInducer20-empty control (=pInd), 40uM ML-60218 treatment (=ML) or DMSO control. each condition has 3 replicates