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.
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: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:To test if LEDGF/p75 influences distribution of Maedi-visna virus (MVV) integration sites, we infected sheep CPT3, LKO1 (PSIP1-null), LHKO1 and LHKO2 (PSIP1/HDGFL2-null) cells with MVV-derived vector. Genomic DNA was isolated from infected cells, and chromosomal junctions at integrated U5 vDNA ends were amplified using linker-mediated PCR, sequenced using Illumina technology and mapped to sheep genome.
Project description:To test if LEDGF/p75 influences distribution of Maedi-visna virus (MVV) integration sites, we infected human HEK293T, LKO (PSIP1-null), and LHKO (PSIP1/HDGFL2-null) cells with MVV-derived vector. Genomic DNA was isolated from infected cells, and chromosomal junctions at integrated U5 vDNA ends were amplified using linker-mediated PCR, sequenced using Illumina technology and mapped to human genome.
Project description:Weâve undertaken a genome-wide approach to identify and test genes in fibroblasts that are both induced upon interaction with basal breast cancer cells in culture and upregulated in stromal cells from primary human breast cancers. Several of the upregulated genes encode secreted growth factors or cytokines. Using RNAi and a co-injection tumorigenicity assay, we determined that the majority of secreted factors selected for functional validation played significant, yet functionally diverse, roles in promoting tumorigenicity. Rather than a single major mediator, these results indicate multiple points of intervention to prevent fibroblasts from supporting basal breast cancer. Additionally, we show that breast cancer subtypes differ markedly in the expression of these and other stromally secreted proteins using data from microdissected stromal samples. Induction of genes in four different fibroblast strains (HFFF2, HFF1, CCD1112Sk and Wi38) upon coculture with Cal51 and MDAMB231 human basal breast cancer cell lines. Monocultures of each group are used as the experimental control with each group having 3-4 independent biological replicates.
Project description:Distinct integration patterns of different retroviruses have puzzled virologists for over 20 years. The viral integrase (IN), as part of the intasome complex, docks onto the target DNA (tDNA) and catalyzes the insertion of the viral genome into the host chromatin. We identified retroviral IN amino acids directly contacting tDNA bases and affecting the local integration site sequence biases. These residues also determine the propensity of the virus to integrate into flexible tDNA sequences. Remarkably, natural polymorphisms INS119G and INR231G retarget viral integration away from gene dense regions, without affecting the interaction with the lentiviral tethering cofactor LEDGF/p75 (PSIP1). Precisely these variants were associated with rapid disease progression in a chronic HIV-1 subtype C infection cohort. These findings link integration site selection to virulence and viral evolution but also to the host immune response and antiretroviral therapy, since HIV-1 IN119 is under selection by HLA alleles and integrase inhibitors. LEDGF/p75 (PSIP1) ChIP-Seq using A300-848 antibody (recognizes p75 isoform) and input control in primary CD4+ T-cells
Project description:We show that the epithelial-like and mesenchymal-like subpopulations of breast cancer stem-like cells (BCSCs) demonstrate different levels dormancy and tumorigenicity in lungs. The long non-coding RNA (lncRNA) molecule NR2F1-AS1 (NAS1) is up-regulated in the dormant BCSC subpopulation, and functionally promotes tumor dissemination but reduces proliferation in lungs. Mechanically, NAS1 promotes internal ribosome entry site (IRES)-mediated NR2F1 translation, leading to inhibition of ΔNp63 transcription by NR2F1. Further, ΔNp63 downregulation results in epithelial-mesenchymal transition, reduced tumorigenicity and enhanced dormancy of cancer cells in lungs.
Project description:The study has been focused on the characterization of the role of LEDGF/p75 in chemiresistance in pediatric leukemia Abstract: MLL is an aggressive subtype of leukemia with a poor prognosis that mostly affects pediatric patients. MLL-rearranged fusion proteins (MLLr) induce aberrant target gene expression resulting in leukemogenesis. MLL and its fusions are tethered to chromatin by LEDGF/p75, a transcriptional co-activator that specifically recognizes H3K36me2/3. LEDGF/p75 is ubiquitously expressed and associated with regulation of gene expression, autoimmune responses and HIV replication. LEDGF/p75 was proven to be essential for leukemogenesis in MLL. Apart from MLL, LEDGF/p75 has been linked to lung, breast and prostate cancer. Intriguingly, LEDGF/p75 interacts with Med-1, which co-localizes with BRD4. Both are known as co-activators of super-enhancers. Here, we describe LEDGF/p75-dependent chemoresistance of MLLr cell lines. Investigation of the underlying mechanism revealed a role of LEDGF/p75 in the cell cycle and in survival pathways and showed that LEDGF/p75 protects against apoptosis during chemotherapy. Remarkably, LEDGF/p75 levels also affected expression of BRD4 and Med1. Altogether, our data suggest a role of LEDGF/p75 in cancer survival, stem cell renewal, and activation of nuclear super enhancers.