Project description:Mixed-lineage leukemia (MLL) represents a genetically distinct and aggressive subset of human acute leukemia carrying chromosomal translocations of the MLL gene. These translocations result in oncogenic fusions that mediate aberrant recruitment of transcription machinery to MLL target genes. The N-terminus of MLL and MLL-fusions form a complex with Lens Epithelium-Derived Growth Factor (LEDGF/p75; encoded by the Psip1 gene) and MENIN. This complex contributes to the association of MLL and MLL-fusion multiprotein complexes with chromatin. Several studies have shown that both MENIN and LEDGF/p75 are required for efficient MLL fusion-mediated transformation and for the expression of downstream MLL-regulated genes like HOXA9 and MEIS1. In light of the development of a therapeutic strategy targeting this complex, understanding the function of LEDGF/p75 in normal hematopoiesis is crucial. We generated a conditional Psip1 knockout mouse model in the hematopoietic compartment and examined the effects of LEDGF/p75 depletion in postnatal hematopoiesis and the initiation of MLL leukemogenesis. Psip1 knockout mice were viable but showed several defects in hematopoiesis, reduced colony-forming activity in vitro, decreased expression of Hox genes in hematopoietic stem cells and decreased MLL occupancy at MLL target genes. Finally, in vitro and in vivo experiments showed that LEDGF/p75 is dispensable for steady state hematopoiesis but essential for the initiation of MLL-mediated leukemia. These data corroborate the MLL-LEDGF/p75 interaction as novel target for the treatment of MLL-rearranged leukemia.
Project description:Menin binding pattern in WT and Psip1 KO MEFs Menin occupancy is studied over Hox genes Menin ChIP from WT and Psip1 KO MEFs ChIP-chip
Project description:Psip1/p75 binds to Hox genes and colocalizes with Mll1 and in Psip1 KO MEFs Mll1 occupancy is reduced over Hox genes Psip1/p75 ChIP using A300-848 abtibody (recognises p75 isoform of Psip1) and Mll1 ChIP from WT and Psip1 KO MEFs ChIP-chip
Project description:Bmi-1, Ring1B, H3K27me3, Ser2 Pol II, Ser 5 Pol II binding pattern in WT and Psip1 KO MEFs Menin occupancy is studied over Hox genes and several non-hox genes Bmi-1, Ring1B, H3K27me3, Ser2 Pol II, Ser 5 Pol II ChIPs from WT and Psip1 KO MEFs
Project description:Bmi-1, Ring1B, H3K27me3, Ser2 Pol II, Ser 5 Pol II binding pattern in WT and Psip1 KO MEFs Menin occupancy is studied over Hox genes and several non-hox genes
Project description:The p52 isoform of Psip1/Ledgf links histone H3K36 methylation and the regulation of alternative splicing. Chromatin immunoprecipitation (ChIP) of Psip1 together with H3K36me3 and H3K4me3 and by ChIP-on-chip analysis demonstrated that, Like H3K36me3, Psip1 is enriched on exons of highly expressed genes, Comparision of H3K36me3 and Psip1 binding sites on the expressed and non expressed genes.
Project description:Breast cancer (BC) is a highly heterogeneous disease, both at the pathological and molecular level, and several chromatin-associated proteins play crucial roles in breast cancer initiation and progression. Here, we demonstrate the role of PSIP1 (PC4 and SF2 interacting protein)/p75 (LEDGF) in breast cancer progression. PSIP1/p75, previously identified as a chromatin-adaptor protein, is found to be upregulated in basal-like/triple negative breast cancer (TNBC) patient samples and cell lines. Immunohistochemistry in tissue arrays showed elevated levels of PSIP1 in metastatic invasive ductal carcinoma. Survival data analyses indicated that the levels of PSIP1 showed a negative association with TNBC patient survival. Depletion of PSIP1/p75 significantly reduced the tumorigenicity and metastatic properties of TNBC cell lines while its over-expression promoted tumorigenicity. Further, gene expression studies revealed that PSIP1 regulates the expression of genes controlling cell-cycle progression, cell migration, and invasion. Finally, by interacting with RNA polymerase II, PSIP1/p75 facilitates the association of RNA pol II to the promoter of cell cycle genes and thereby regulates their transcription. Our findings demonstrate an important role of PSIP1/p75 in TNBC tumorigenicity by promoting the expression of genes that control the cell cycle and tumor metastasis.
