Poly(C)-Binding Protein Pcbp2 Enables Differentiation of Definitive Erythropoiesis by Directing Functional Splicing of the Runx1 Transcript

Abstract

Formation of the mammalian hematopoietic system is under a complex set of developmental controls. Here, we report that mouse embryos lacking the KH domain poly(C) binding protein, Pcbp2, are selectively deficient in the definitive erythroid lineage. Compared to wild-type controls, transcript splicing analysis of the Pcbp2 embryonic liver reveals accentuated exclusion of an exon (exon 6) that encodes a highly conserved transcriptional control segment of the hematopoietic master regulator, Runx1. Embryos rendered homozygous for a Runx1 locus lacking this cassette exon (Runx1ΔE6) effectively phenocopy the loss of the definitive erythroid lineage in Pcbp2 embryos. These data support a model in which enhancement of Runx1 cassette exon 6 inclusion by Pcbp2 serves a critical role in development of hematopoietic progenitors and constitutes a critical step in the developmental pathway of the definitive erythropoietic lineage.

Analysis of eEF1Bγ interactome in the nuclear fraction of A549 human lung adenocarcinoma cells

“…Protein PCBP2 (Poly(rC) binding protein 2) is a splicing factor [18], it participates in signal transduction pathways [19]. PCBP2 is a negative regulator of IRES-mediated mRNA translation [20].…”

Heterogeneous nuclear ribonucleoprotein K is overexpressed in acute myeloid leukemia and causes myeloproliferative disease in mice via altered Runx1 splicing

“…The Runx1ΔEx6 isoform exhibits higher self-renewal capacity in colony formation assays, which is in agreement with the findings of Komeno et al and Sun et al (Komeno et al, 2014; Sun et al, 2020). In addition, others have demonstrated a depletion in the cellular pool of HSCs in vivo in mice lacking the RUNX1ΔEx6 isoform, indicating the importance of tight regulation of splicing in hematopoiesis (Ghanem et al, 2018; Komeno et al, 2014).…”

“…RUNX1 is a common target of translocations or mutations in leukemias, including AML (De Braekeleer et al, 2011; Osato, 2004; Osato et al, 1999). Interestingly, expression of different RUNX1 isoforms arising via alternative splicing, specifically around exon 6, also alter hematopoiesis (Ghanem et al, 2018; Komeno et al, 2014; Sun et al, 2020).…”

Systematic profiling of a novel prognostic alternative splicing signature in hepatocellular carcinoma

“…Poly(C)-binding protein 2 (PCBP2), as a multifunctional adapter that contributes to mRNA stabilization, translational silencing and enhancement via the poly(C)-binding motif, has been widely reported to mediate ambiguous functions in various types of cancer, including gastric cancer, breast cancer, pancreatic ductal adenocarcinoma, esophageal squamous cell carcinoma and glioblastoma (37,64–68). A particular AS event was also implicated in the presence of the binding site of PCBP2 within the exon 6 splicing acceptor (69). PCBP2 is pivotal in attenuating the innate immune response against hepatitis C infection and promoting alcoholic liver fibrosis, both of which are recognized as clinical carcinogenic factors for HCC (70,71).…”