Disruption of RING and PHD Domains of TRIM28 Evokes Differentiation in Human iPSCs

TRIM28, a multi-domain protein, is crucial in the development of mouse embryos and the maintenance of embryonic stem cells’ (ESC) self-renewal potential. As the epigenetic factor modulating chromatin structure, TRIM28 regulates the expression of numerous genes and is associated with progression and poor prognosis in many types of cancer. Because of many similarities between highly dedifferentiated cancer cells and normal pluripotent stem cells, we applied human induced pluripotent stem cells (hiPSC) as a model for stemness studies. For the first time in hiPSC, we analyzed the function of individual TRIM28 domains. Here we demonstrate the essential role of a really interesting new gene (RING) domain and plant homeodomain (PHD) in regulating pluripotency maintenance and self-renewal capacity of hiPSC. Our data indicate that mutation within the RING or PHD domain leads to the loss of stem cell phenotypes and downregulation of the FGF signaling. Moreover, impairment of RING or PHD domain results in decreased proliferation and impedes embryoid body formation. In opposition to previous data indicating the impact of phosphorylation on TRIM28 function, our data suggest that TRIM28 phosphorylation does not significantly affect the pluripotency and self-renewal maintenance of hiPSC. Of note, iPSC with disrupted RING and PHD functions display downregulation of genes associated with tumor metastasis, which are considered important targets in cancer treatment. Our data suggest the potential use of RING and PHD domains of TRIM28 as targets in cancer therapy.

The PHD transcription factor Cti6 is involved in the fungal colonization and aflatoxin B1 biological synthesis of Aspergillus flavus

Aspergillus flavus and its main secondary metabolite AFB1 pose a serious threat to several important crops worldwide. Recently, it has been reported that some PHD family transcription factors are involved in the morphogenesis and AFB1 biological synthesis in A. flavus, but the role of Cti6, a PHD domain containing protein in A. flavus, is totally unknown. The study was designed to reveal the biological function of Cti6 in the fungus by deletion of cti6, and its two domains (PHD and Atrophin-1) through homologous recombination, respectively. The results showed that Cti6 might up-regulate the mycelium growth, conidiation, sclerotia formation and AFB1 biological synthesis of A. flavus by its PHD domain, while Atrophin-1 also improved the conidiation of the fungus. The qRT-PCR analysis showed that Cti6 increased the conidiation of the fungus through AbaA and BrlA mediated conidiation pathway, triggered the formation of sclerotia by orthodox sclerotia formation pathway, and improved the production of AFB1 by orthodox AFB1 synthesis pathway. Crops models analysis showed that A. flavus Cti6 plays vital role in colonization and the production of AFB1 on the host grains mainly via PHD domain. Bioinformatics analysis showed Cti6 is conservative in Aspergillus spp., and mCherry mediated subcellular localization showed that most Cti6 accumulated in the nuclei, which reflected that Cti6 performed its important biological function in the nuclei in Aspergillus spp.. The results of the current study elucidate the roles of PHD domain containing proteins in the mechanism of the infection of crops by A. flavus, and provided a novel target for effectively controlling the contamination of Aspergillus spp. to crops.

The PHD Transcription Factor Cti6 is Involved in the Fungal Colonization and Aflatioxin B1 Biological Synthesis of Aspergillus Flavus

Aspergillus flavus and its main secondary metabolite AFB1 pose a serious threat to several important crops worldwide. Recently, it has been reported that some PHD family transcription factors are involved in the morphogenesis and AFB1 biological synthesis in A. flavus, but the role of Cti6, a PHD domain containing protein in A. flavus, is totally unknown. The study was designed to reveal the biological function of Cti6 in the fungus by deletion of cti6, and its two domains (PHD and Atrophin-1) through homologous recombination, respectively. The results showed that Cti6 might up-regulate the mycelium growth, conidiation, sclerotia formation and AFB1 biological synthesis of A. flavus by its PHD domain, while Atrophin-1 also improved the conidiation of the fungus. The qRT-PCR analysis showed that Cti6 increased the conidiation of the fungus through AbaA and BrlA mediated conidiation pathway, triggered the formation of sclerotia by orthodox sclerotia formation pathway, and improved the production of AFB1 by orthodox AFB1 synthesis pathway. Crops models analysis showed that A. flavus Cti6 plays vital role in colonization and the production of AFB1 on the host grains mainly via PHD domain. Bioinformatics analysis showed Cti6 is conservative in Aspergillus spp., and mCherry mediated subcellular localization showed that most Cti6 accumulated in the nuclei, which reflected that Cti6 performed its important biological function in the nuclei in Aspergillus spp.. The results of the current study elucidate the roles of PHD domain containing proteins in the mechanism of the infection of crops by A. flavus, and provided a novel target for effectively controlling the contamination of Aspergillus spp. to crops.

STAG2-mutated AML patients: ASXL1 cohesin binding motif status and mutation landscape.

7538 Background: ASXL1 and the cohesin complex ( STAG2, RAD21, SMC1A, and SMC3) are commonly mutated chromatin regulators with significant clinical implications in AML. The ASXL1-cohesin interactome regulates gene expression through chromatin accessibility via ASXL1’s cohesin binding motif (CBM). ASXL1 variants are most commonly located in the ASXM1 domain and onwards, and characteristically lead to loss of the PHD domain. Gain-of-functions in truncated ASXL1 are suggested to increase catalytic activity of BAP1, which binds the ASXH domain at AA 351, and to gain an interaction with BRD4, which binds somewhere between the ASXN and ASXH domains, to drive H3K4Me3 and H2AK119Ub. Methods: 2463 suspected AML patient bone marrow, peripheral blood, or FFPE tissue samples were evaluated using an all exon amplicon-based 27 gene NGS panel. Patients with a VAF <10% in ASXL1 were excluded to avoid reporting artifacts, particularly in variant c. 1934dup. Statistics were performed using Fisher’s exact test. Results: Mutations in STAG2-mutated patients were enriched for sAML, as evidenced by the higher number of mutations in ASXL1, SRSF2, and BCOR (associated with sAML) compared to NPM1, DNMT3A, and PTPN11 (pAML). STAG2 mutations were found in 173 samples representing 93.5% of cohesin mutations. Of all ASXL1 mutations (VAF 10.1– 54.5%; median 32.2%) 4.0% occurred in the CBM. While 23.5% of samples with mutations outside ASXL1 CBM had concomitant mutations in STAG2, none of the 18 samples with CBM mutations (VAF 11.3 – 51.7%; median 42.5%) had any cohesin gene mutation (P = 0.0174). The proportion of BCOR (27.8% vs 9.2%; P = 0.024) and CEBPA (27.8% vs 8.2%; p = 0.016) mutated patients in the CBM+ group was significantly higher than the CBM- group. JAK2 (16.7% vs 5.4%), KRAS (22.2% vs 13.6%), EZH2 (22.2% vs 13.6%), and RUNX1 (38.9% vs 27.7%) mutations were also higher though not significantly in this group. Mutations throughout all of ASXL1, the 13 amino acids after the CBM, and hotspot variants all had STAG2 mutations at a frequency of 20.9-44.4%, further suggesting mutual exclusivity. Conclusions: STAG2 mutations and mutations in the CBM were mutually exclusive events and harbored different co-mutation frequencies. In compromised ASXL1 CBM cases, BCOR and CEBPA transcriptional regulators are significantly more mutated, but in cases of ASXL1 mutation outside the CBM, cohesin mutations are preferred, suggesting alternative chromatin accessibility mechanisms driving leukemogenesis. This observation has not been previously reported in the literature to our knowledge.

The histone H3K4 demethylase JARID1A directly interacts with haematopoietic transcription factor GATA1 in erythroid cells through its second PHD domain

Chromatin remodelling and transcription factors play important roles in lineage commitment and development through control of gene expression. Activation of selected lineage-specific genes and repression of alternative lineage-affiliated genes result in tightly regulated cell differentiation transcriptional programmes. However, the complex functional and physical interplay between transcription factors and chromatin-modifying enzymes remains elusive. Recent evidence has implicated histone demethylases in normal haematopoietic differentiation as well as in malignant haematopoiesis. Here, we report an interaction between H3K4 demethylase JARID1A and the haematopoietic-specific master transcription proteins SCL and GATA1 in red blood cells. Specifically, we observe a direct physical contact between GATA1 and the second PHD domain of JARID1A. This interaction has potential implications for normal and malignant haematopoiesis.