Abstract
Monoubiquitination of core histone 2A (H2A-K119u) has a critical role in gene regulation in hematopoietic differentiation and other developmental processes. To explore the interplay of histone H2A deubiquitinase Myb-like SWIRM and MPN domain containing1 (2A-DUB/Mysm1) with the p53 axis in the sequential differentiation of mature lymphocytes from progenitors, we systematically analyzed hematopoiesis and early T-cell development using Mysm1−/− and p53−/−Mysm1−/− mice. Mysm1−/− thymi were severely hypoplastic with <10% of wild-type cell numbers as a result of a reduction of early thymocyte progenitors in context with defective hematopoietic stem cells, a partial block at the double-negative (DN)1–DN2 transition and increased apoptosis of double-positive thymocytes. Increased rates of apoptosis were also detected in other tissues affected by Mysm1 deficiency, including the developing brain and the skin. By quantitative PCR and chromatin immunoprecipitation analyses, we identified p19ARF, an important regulator of p53 tumor suppressor protein levels, as a potential Mysm1 target gene. In newly generated p53−/−Mysm1−/− double-deficient mice, anomalies of Mysm1−/− mice including reduction of lymphoid-primed multipotent progenitors, reduced thymocyte numbers and viability, and interestingly defective B-cell development, growth retardation, neurological defects, skin atrophy, and tail malformation were almost completely restored as well, substantiating the involvement of the p53 pathway in the alterations caused by Mysm1 deficiency. In conclusion, this investigation uncovers a novel link between H2A deubiquitinase 2A-DUB/Mysm1 and suppression of p53-mediated apoptotic programs during early lymphoid development and other developmental processes.
Highlights
In a quantitative PCR screening approach, we identified 2A-DUB/Mysm[1] as a gene expressed throughout the double-negative (DN) 1–4 populations in the thymus, in double-positive (DP), single-positive (SP)[4], and SP8 thymocytes, and regulated by stimulation with T-cell receptor (TCR) agonists, such as anti-CD3, in thymocytes and peripheral T cells in vitro, as well as by inducers of apoptosis and DNA damage such as etoposide and γ-irradiation, in thymocytes (Figure 1a)
As cellularities of bone marrow (BM) and lymphoid organs were partially restored in p53− / −Mysm1− / − DKO mice, we subsequently examined the presence of stem cell populations and lymphoid progenitors in the BM and of mature B cells in peripheral lymphoid organs of 4-week-old DKO mice and age-matched littermates
The major finding of the present investigation is that histone H2A deubiquitinase 2A-DUB/Mysm[1] is critically required in lymphoid progenitors, developing thymocytes, and other cell types for protection from p53-mediated apoptotic programs
Summary
According to the histone code model of transcriptional regulation, collaboration of histone modifying and chromatin remodeling enzymes with sequence-specific DNA binding transcription factors (TFs) in larger multiprotein complexes is required for the sequential differentiation of specialized cell populations from their progenitors, to activate and silence lineage-specific genes in a coordinated manner.[1,2,3,4] In this context, chromatin remodeling complexes of the SWI/SNF, ISWI and Mi-2/NuRD families control the accessibility of specific regions of DNA to lineage-specific TFs by regulating chromatin compaction, spacing of nucleosomes, histone– DNA contacts, and association with histone modifying enzymes.[5,6,7,8,9] aside from DNA methylation, covalent posttranslational modifications of the four core histones (H2A, H2B, H3, and H4) – including acetylation, methylation, phosphorylation, sumoylation, and ubiquitination – regulate target gene accessibility via introduction of permissive or repressive marks.[10,11]. Components of the Polycomb Repressive Complex (PRC) 1, such as Bmi[1], Mel[18], and Ring1a/b, which recognizes trimethylated Histone H3 (3mH3K27) and competitively inhibits the SWI/SNF–chromatin remodeling complex, are established regulators of hematopoietic stem cell (HSC) maintenance and T-cell development.[12,13] In a heterodimetric complex with Bmi[1], Ring1b possesses significant E3 ubiquitin ligase activity and mediates Polycomb silencing and. H2A deubiquitinases (H2A-DUBs), such as USP3 (Nicasso et al.,22), USP16/Ubp-M,23,24 USP21, (Nakagawa et al.25), USP22 (Zhang et al.,26) and 2A-DUB,[27] in context with co-activator complexes.[28,29] As per the current concept, H2A ubiquitination contributes to specific transcriptional repression programs, maintenance of genome stability, and DNA repair, whereas H2A deubiquitination is associated with transcriptional activation, cell cycle transition, as well as tuning of genome stability and target gene activation in cancer cells.[29,30].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
