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Asrij/OCIAD1 suppresses CSN5-mediated p53 degradation and maintains mouse hematopoietic stem cell quiescence

Saloni Sinha, Tirath Raj Dwivedi, Roja Yengkhom, Venkata Anudeep Bheemsetty, Takaya Abe, Hiroshi Kiyonari, K VijayRaghavan and Maneesha S Inamdar

Key Points

  • Asrij interacts with COP9 signalosome subunit CSN5 to prevent MDM2-mediated p53 degradation and maintains mouse bone marrow HSC quiescence

  • Asrij is a novel regulator of wild type p53 stability in HSCs and could help design targeted therapies for myeloproliferative disease

Abstract

Inactivation of the tumor suppressor p53 is essential for unrestrained growth of cancers. However, only 11% of hematological malignancies have mutant p53. Mechanisms that cause wild type p53 dysfunction and promote leukemia are inadequately deciphered. The stem cell protein Asrij/OCIAD1 is misexpressed in several human hematological malignancies and implicated in the p53 pathway and DNA damage response. However, Asrij function in vertebrate hematopoiesis remains unknown. We generated the first asrij null (knockout, KO) mice and show that they are viable and fertile with no gross abnormalities. However, by six months, they exhibit increased peripheral blood cell counts, splenomegaly and an expansion of bone marrow hematopoietic stem cells (HSCs) with higher myeloid output. HSCs lacking Asrij are less quiescent and more proliferative with higher repopulation potential as observed from serial transplantation studies. However, stressing KO mice with sub-lethal gamma irradiation or multiple injections of 5-fluorouracil results in reduced survival and rapid depletion of hematopoietic stem/progenitor cells (HSPCs) by driving them into proliferative exhaustion. Molecular and biochemical analyses revealed increased polyubiquitinated protein levels, Akt/STAT5 activation and CSN5 (COP9 signalosome subunit 5)-mediated p53 ubiquitination and degradation in KO HSPCs. Further, we show that Asrij sequesters CSN5 via its conserved OCIA domain, thereby preventing p53 degradation. In agreement, Nutlin-3 treatment of KO mice restored p53 levels and reduced high HSPC frequencies. Thus, we provide a new mouse model resembling myeloproliferative disease and identify a post-translational regulator of wild type p53 essential for maintaining HSC quiescence that could be a potential target for pharmacological intervention.

  • Submitted March 10, 2019.
  • Revision received March 19, 2019.
  • Accepted April 4, 2019.