Efficient globin production during terminal erythropoiesis in mice depends on the cooperative action of TENT5C poly(A) polymerase and LARP4B

Red blood cell development is a unique process in which reduced transcriptome and proteome complexity enable extensive hemoglobin production. Here, we describe the cooperative roles of cytoplasmic poly(A) polymerase TENT5C and the poly(A) tail-protecting LARP4B RNA-binding protein in ensuring proper hemoglobin synthesis. TENT5C catalytic mutant knock-in mice exhibit microcytic hypochromic anemia similar to that observed in the constitutive knockout. Through poly(A) tail extension, TENT5C counteracts the gradual deadenylation of globin mRNA during erythropoiesis. In the late stages, TENT5C dysfunction results in globin poly(A) tail shortening and a pronounced reduction in mRNA levels in reticulocytes. Proteomic experiments reveal a transient but specific association of TENT5C with LARP4B. Consistent with this interaction, LARP4B depletion results in reduced globin mRNA abundance and shortened poly(A) tails, which expands the known physiological roles of this RNA-binding protein. Furthermore, we show that TENT5C is a highly unstable protein whose stability is partially dependent on CNOT4, a deadenylase-associated E3 ubiquitin ligase. In mice, the cytoplasmic poly(A) polymerase TENT5C and RNA-binding protein LARP4B cooperatively protect and re-extend globin mRNA poly(A) tails during terminal erythropoiesis, sustaining hemoglobin production. Deficiency of either factor results in microcytic anemia.