The non-canonical poly(A) polymerase FAM46C promotes erythropoiesis [RIP]
Posttranscriptional regulation of mRNA is a crucial component of gene expression. The disruption of this process can have detrimental effects on normal development and give rise to various diseases.  The search for novel posttranscriptional regulators and the exploration of their roles are essential for understanding development and disease. Through a multimodal analysis of red blood cell trait GWASs and transcriptomes of erythropoiesis, we identified FAM46C, a non-canonical RNA poly(A) polymerase, as a necessary factor for proper red blood cell development. FAM46C is highly expressed in late stages of the erythroid lineage, and its developmental upregulation is controlled by an erythroid-specific enhancer. We demonstrate that FAM46C stabilizes mRNA in an enzyme activity dependent manner by maintaining the poly(A) tails of its targets. Furthermore, we identified transcripts of lysosome and mitochondria components as highly confident in vivo targets of FAM46C, which aligns with the need of maturing red blood cells for substantial clearance of organelles and maintenance of cellular redox homeostasis. In conclusion, our study unveils a novel role of FAM46C in positively regulating the level of lysosome and mitochondria components, thereby promoting erythropoiesis. Overall design: RNA Immunoprecipitation Sequencing (RIP-seq) for FAM46C-strep in HUDEP-2 cells