ANP32B-mediated repression of p53 contributes to maintenance of normal and CML stem cells.

Proper regulation of p53 signaling is critical for the maintenance of hematopoietic stem cells (HSCs) and leukemic stem cells (LSCs). The hematopoietic cell-specific mechanisms regulating p53 activity remain largely unknown. Here, we demonstrate that conditional deletion of acidic leucine-rich nuclear phosphoprotein 32B (ANP32B) in hematopoietic cells impairs repopulation capacity and postinjury regeneration of HSCs. Mechanistically, ANP32B forms a repressive complex with p53 and thus inhibits the transcriptional activity of p53 in hematopoietic cells, and p53 deletion rescues the functional defect in Anp32b-deficient HSCs. Of great interest, ANP32B is highly expressed in leukemic cells from patients with chronic myelogenous leukemia (CML). Anp32b deletion enhances p53 transcriptional activity to impair LSC function in a murine CML model and exhibits synergistic therapeutic effects with tyrosine kinase inhibitors in inhibiting CML propagation. In summary, our findings provide a novel strategy to enhance p53 activity in LSCs by inhibiting ANP32B and identify ANP32B as a potential therapeutic target in treating CML.

Targeting USP47 overcomes tyrosine kinase inhibitor resistance and eradicates leukemia stem/progenitor cells in chronic myelogenous leukemia.

Identifying novel drug targets to overcome resistance to tyrosine kinase inhibitors (TKIs) and eradicating leukemia stem/progenitor cells are required for the treatment of chronic myelogenous leukemia (CML). Here, we show that ubiquitin-specific peptidase 47 (USP47) is a potential target to overcome TKI resistance. Functional analysis shows that USP47 knockdown represses proliferation of CML cells sensitive or resistant to imatinib in vitro and in vivo. The knockout of Usp47 significantly inhibits BCR-ABL and BCR-ABLT315I-induced CML in mice with the reduction of Lin-Sca1+c-Kit+ CML stem/progenitor cells. Mechanistic studies show that stabilizing Y-box binding protein 1 contributes to USP47-mediated DNA damage repair in CML cells. Inhibiting USP47 by P22077 exerts cytotoxicity to CML cells with or without TKI resistance in vitro and in vivo. Moreover, P22077 eliminates leukemia stem/progenitor cells in CML mice. Together, targeting USP47 is a promising strategy to overcome TKI resistance and eradicate leukemia stem/progenitor cells in CML.

Author Correction: PTENα and PTENß promote carcinogenesis through WDR5 and H3K4 trimethylation.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

PTENα and PTENß promote carcinogenesis through WDR5 and H3K4 trimethylation.

PTENα and PTENß are two longer translational variants of phosphatase and tensin homolog (PTEN) messenger RNA. Their expressional regulations and functions in carcinogenesis remain largely unknown. Here, we demonstrate that, in contrast with the well-established tumour-suppressive role of canonical PTEN, PTENα and PTENß promote tumourigenesis by directly interacting with the histone H3 lysine 4 (H3K4) presenter WDR5 to promote H3K4 trimethylation and maintain a tumour-promoting signature. We also show that USP9X and FBXW11 bind to the amino-terminal extensions of PTENα/ß, and respectively deubiquitinate and ubiquitinate lysines 235 and 239 in PTENα to regulate PTENα/ß stability. In accordance, USP9X promotes tumourigenesis and FBXW11 suppresses tumourigenesis through PTENα/ß. Taken together, our results indicate that the Pten gene is a double-edged sword for carcinogenesis, and reinterpretation of the importance of the Pten gene in carcinogenesis is warranted.

[A novel mutation of the alpha-L-iduronidase gene in a patient with mucopolysaccharidosis type I].

OBJECTIVE: To investigate the molecular genetic mechanism of a Chinese patient with mucopolysaccharidosis type I (MPS I). METHODS: PCR-sequencing analysis was applied to detect the mutations in exons in alpha-L-iduronidase gene (IDUA) of the patient. Restriction fragment length polymorphism (RFLP) and allele-specific oligonucleotide hybridization (ASO) were used to confirm the identified mutations. PCR amplified DNA samples from 50 normal individuals were sequenced to demonstrate that the newly identified mutation was not polymorphism. RESULTS: The patient was compound heterozygous for a previously reported nonsense mutation Q60X (178C > T) in exon 2, inherited from the mother, and a newly detected missense mutation D203N (607G > A) in exon 6 from the father. The newly identified mutation D203N was not found in PCR amplified products from 50 normal individuals, indicating that it was not polymorphism. CONCLUSION: The two identified mutations may be the cause resulting in patient's clinical phenotype.

[Detection of two novel mutations of iduronate-2-sulfatase gene in patients with mucopolysaccharidosis type II].

In the present study, through PCR amplification and direct sequencing of mutation "hotspots", we were able to identify two novel mutations in the human iduronate-2-sulfatase (IDS) gene in two patients from unrelated families with mucopolysaccharidosis type II(MPS II). The novel mutation IVS 6 -1g-->a affected the 3' splice acceptor site of intron 6, and was predicted to result in exon skipping. The novel mutation c.1587-1588 ins T involved a single base insertion be-tween nucleotides 1,587 and 1,588 in exon 9, and was predicted to result in frame shift and premature termination. The two novel mutations did not occur in 6 other unrelated MPS patients or in 100 alleles from normal individuals, indicating that they were not polymorphisms. The PCR-restriction enzyme digestion showed that the two newly identified mutations were of maternal origin, which was consistent with the X-linked recessive disorder. These findings suggest that the IDS gene mutations could be detected by amplifying mutation "hotspots", direct sequencing and restriction digestion analysis, and the newly identified mutations may be disease-causing.

Skeletal myogenesis by human embryonic stem cells.

We have examined the myogenic potential of human embryonic stem (hES) cells in a xeno-transplantation animal model. Here we show that precursors differentiated from hES cells can undergo myogenesis in an adult environment and give rise to a range of cell types in the myogenic lineage. This study provides direct evidences that hES cells can regenerate both muscle and satellite cells in vivo and are another promising cell type for treating muscle degenerative disorders in addition to other myogenic cell types.