Elucidating an Erythroblast Survival Mechanism: Differential Contributions of Exosome Complex Catalytic Subunits

• Published in: Blood 2019-11, Vol.134 (Supplement_1), p.155-155
• Main Authors: Mehta, Charu, Fraga de Andrade, Isabela J, Tanimura, Nobuyuki, Wilson, Gary M, Ranheim, Erik A., Coon, Joshua J, Bresnick, Emery H
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2019-126917

The 11-subunit exosome complex (EC) controls the degradation, processing and synthesis of non-coding and coding RNAs. Although EC actions on RNAs can be highly selective, it regulates fundamental biological processes including the DNA damage response, maintenance of genome integrity, stem cell differentiation and erythroid maturation. The EC catalytic subunits Exosc10 and Dis3 degrade RNAs in the nucleus. DIS3 is mutated frequently in human multiple myeloma (Chapman et al., Nature, 2011), although the dysregulated RNA targets are not established. McIver et al. (Blood, 2014, eLife, 2016), demonstrated that EC is an important determinant of erythroid progenitors (BFU-E) and c-Kit signaling. While structural requirements for EC formation and activity are defined, how EC controls processes such as cellular proliferation, survival and differentiation is unclear. During erythropoiesis, the master regulator of erythrocyte development GATA1 represses genes encoding EC subunits. We conducted a multiomic analysis of GATA1-regulated transcripts and proteins in a genetic complementation system (Tanimura et al., Dev. Cell, 2018), which revealed a disproportionately greater loss of EC catalytic subunits Exosc10 and Dis3 (~5 fold), in comparison with other EC subunits, during erythroid maturation. As it is unclear if one or both catalytic subunits are required to generate BFU-E, and EC catalytic subunit functions have not been analyzed in other progenitor contexts, we tested whether the catalytic subunits function similarly or differentially. We conducted loss-of-function studies using shRNAs to downregulate Dis3 or Exosc10 in primary mouse fetal liver cells. Loss of Dis3 mRNA did not impact Exosc10 expression and vice versa. Two shRNAs against Dis3 almost entirely ablated BFU-E, CFU-GM and CFU-GEMM (>90%, p < 0.0001), whereas two shRNAs against Exosc10 decreased BFU-E and CFU-GM by 65 and 55% (p