Identification of Chromatin Remodeling Genes Arid4a and Arid4b as Leukemia Suppressor Genes

Abstract

BackgroundLeukemia evolves through a multistep process from premalignancy to malignancy. Epigenetic alterations, including histone modifications, have been proposed to play an important role in tumorigenesis. The involvement of two chromatin remodeling genes, retinoblastoma-binding protein 1 (Rbbp1/Arid4a) and Rbbp1-like 1 (Rbbp1l1/Arid4b), in leukemogenesis was not characterized.MethodsThe leukemic phenotype of mice deficient for Arid4a with or without haploinsufficiency for Arid4b was investigated by serially monitoring complete blood counts together with microscopic histologic analysis and flow cytometric analysis of bone marrow and spleen from the Arid4a−/− mice or Arid4a−/−Arid4b+/− mice. Regulation in bone marrow cells of downstream genes important for normal hematopoiesis was analyzed by reverse transcription–polymerase chain reaction. Genotypic effects on histone modifications were examined by western blotting and immunofluorescence analysis. All statistical tests were two-sided.ResultsYoung (2–5 months old) Arid4a-deficient mice had ineffective blood cell production in all hematopoietic lineages. Beyond 5 months of age, the Arid4a−/− mice manifested monocytosis, accompanied by severe anemia and thrombocytopenia. These sick Arid4a−/− mice showed bone marrow failure with myelofibrosis associated with splenomegaly and hepatomegaly. Five of 42 Arid4a−/− mice and 10 of 12 Arid4a−/−Arid4b+/− mice progressed to acute myeloid leukemia (AML) and had rapid further increases of leukocyte counts. Expression of Hox genes (Hoxb3, Hoxb5, Hoxb6, and Hoxb8) was decreased in Arid4a-deficient bone marrow cells with or without Arid4b haploinsufficiency, and FoxP3 expression was reduced in Arid4a−/−Arid4b+/− bone marrow. Increases of histone trimethylation of H3K4, H3K9, and H4K20 (fold increases in trimethylation = 32, 95% confidence interval [CI] = 27 to 32; 45, 95% CI = 41 to 49; and 2.2, 95% CI = 1.7 to 2.7, respectively) were observed in the bone marrow of Arid4a-deficient mice.ConclusionsArid4a-deficient mice initially display ineffective hematopoiesis, followed by transition to chronic myelomonocytic leukemia (CMML)–like myelodysplastic/myeloproliferative disorder, and then transformation to AML. The disease processes in the Arid4a-deficient mice are very similar to the course of events in humans with CMML and AML. This mouse model has the potential to furnish additional insights into the role of epigenetic alterations in leukemogenesis, and it may be useful in developing novel pharmacological approaches to treatment of preleukemic and leukemic states.

Retinoblastoma-binding Protein 1 Has an Interdigitated Double Tudor Domain with DNA Binding Activity

“…Retinoblastoma-binding protein 1 (RBBP1) 3 and its homolog RBBP1-like protein 1 (RBBP1L1) are leukemia and tumor suppressors that specifically interact with retinoblastoma protein (RB) and the mSin3A complex to suppress gene repression (1)(2)(3)(4)(5)(6)(7)(8). Peptide sequences, including KASIFLK in RBBP1 (9) and SSKKQKRSHK and IKPSLGSKK in RBBP1L1 (6,10), have been identified as breast carcinoma antigen epitopes.…”

“…Peptide sequences, including KASIFLK in RBBP1 (9) and SSKKQKRSHK and IKPSLGSKK in RBBP1L1 (6,10), have been identified as breast carcinoma antigen epitopes. RBBP1 and RBBP1L1 regulate epigenetic marks, such as methylation of lysines in histones H3 and H4, which are observed in leukemia and Prader-Willi/Angelman syndromes (2,11). The epigenetic regulation function of RBBP1 was proposed to be mediated by its three Royal Family domains (2,11,12), including the chromobarrel domain, Tudor domain, and Pro-Trp-Trp-Pro (PWWP) domain, but our previous study indicated that of these three domains, only the chromobarrel domain can bind with histone tails and is responsible for the epigenetic regulation function (13).…”

Human Family with Sequence Similarity 60 Member A (FAM60A) Protein: a New Subunit of the Sin3 Deacetylase Complex

“…For example, breast cancer metastasis suppressor 1 (BRMS1) can suppress metastasis of cancer in mouse models (18). In addition, ING1 and retinoblastoma binding protein 1 (RBP1) display tumor suppressive properties (19,20). Moreover, some Sin3 complex subunits may display both tumor suppressive and oncogenic properties depending on the context (i.e.…”

A Novel Function of RNAs Arising From the Long Terminal Repeat of Human Endogenous Retrovirus 9 in Cell Cycle Arrest

“…2Aa knock down these transcription factors. BRCAA1 is a known tumor suppressor gene, since its deficiency in mice leads to leukemia (32), and mutations in this gene contribute to development of human diseases and cancer through epigenetic mechanisms (32). However, given that the 549-nt AS RNA is embedded in BRCAA1 intronic elements, it is tempting to speculate that one potential mechanism of the tumor suppression mediated by BRCAA1 gene pertains to potential antiproliferative activity of this AS species, which contains NF-Y binding sites.…”

“…RNAs were separated on 12% denaturing urea-polyacryamide gels and transferred to a nylon membrane. S and AS ODN probes end labeled with 32 P were used to detect AS and S endogenous U3 RNAs separately. RNAs of four matched pairs of human breast cancer and adjacent normal mammary tissues were obtained from Indivumed.…”