Transcription profiling of human monocytes infected with adenovirus expressing either c-Myb or v-Myb
ABSTRACT: The transcriptional activities of c-Myb and its oncogenic variant v-Myb were compared by expressing them in primary human monocytes using recombinant adenovirus vectors. All the samples were compared to cells infected with a control adenovirus expressing only GFP. The results showed that v-Myb, which differs from c-Myb only by N- and C-terminal deletions and eleven amino acid substitutions, has a qualitatively different transcriptional activity. Experiment Overall Design: 2 replicates of each type were analyzed. Replicates were performed independently, more than a week apart.
The v-Myb oncoprotein encoded by Avian Myeloblastosis Virus is highly oncogenic, induces leukemias in chickens and mice and transforms immature hematopoietic cells in vitro. The v-Myb protein is a mutated and truncated version of c-Myb, a DNA-binding transcription factor expressed in many cell types that is essential for normal hematopoiesis. Previous studies suggested that two types of differences, DNA binding domain mutations and the deletion of a C-terminal negative regulatory domain were imp ...[more]
Project description:The transcriptional activities of c-Myb and its oncogenic variant v-Myb were compared by expressing them in human MCF7 cells using recombinant adenovirus vectors. A hybrid construct, 3Mutc, which is a variant of c-Myb harboring three v-Myb-derived DNA binding domain mutations was also analyzed. All the samples were compared to cells infected with a control adenovirus. The results showed that v-Myb, which differs from c-Myb only by N- and C-terminal deletions and eleven amino acid substitutions, has a qualitatively different transcriptional activity. Experiment Overall Design: 2 replicates of each type were analyzed. Replicates were performed independently, more than a week apart.
Project description:Recombinant adenovirus vectors were used to express wild type or domain swap mutants of A-Myb and c-Myb transcription factors in MCF-7 cells or pimary lung epithelial cells or fibroblasts. The results show that Myb proteins have extreme context specificity and identify sub-domains responsible for the activation of specific sets of target genes.
Project description:Most E2F-binding sites repress transcription through the recruitment of Retinoblasoma (RB) family members until the end of the G1 cell-cycle phase. Although the MYB promoter contains an E2F-binding site, its transcription is activated shortly after the exit from quiescence, before RB family members inactivation, by unknown mechanisms. We had previously uncovered a nuclear factor distinct from E2F, Myb-sp, whose DNA-binding site overlapped the E2F element and had hypothesized that this factor might overcome the transcriptional repression of MYB by E2F-RB family members. We have purified Myb-sp and discovered that Myc-associated zinc finger proteins (MAZ) are major components. We show that various MAZ isoforms are present in Myb-sp and activate transcription via the MYB-E2F element. Moreover, while forced RB or p130 expression repressed the activity of a luciferase reporter driven by the MYB-E2F element, co-expression of MAZ proteins not only reverted repression, but also activated transcription. Finally, we show that MAZ binds the MYB promoter in vivo, that its binding site is critical for MYB transactivation, and that MAZ knockdown inhibits MYB expression during the exit from quiescence. Together, these data indicate that MAZ is essential to bypass MYB promoter repression by RB family members and to induce MYB expression.
Project description:Low levels of MYB promote the development of myeloproliferative neoplasm (MPN). The cell type identified that can transplant the MPN phenotype has been identified as expressing KIT, CD11b and low levels of lineage markers (K11bL). We sought to identify changes in gene expression between wild type and MYB knockdown K11bL cells to identify potential targets of MYB that play a role in the establishment of MPN. Overall design: 4 week old male wild type and MYB knockdown mice (three mice per group) were sacrificed and Kit+CD11b+Lin-Low (K11bL) cells were sorted by FACS from their bone marrow. RNA was extracted and hybridised on Affymetrix microarrays.
Project description:Using an integrative approach combining a Tet-off conditional AML mouse model, global expression profiling following suppression of the driving MLL-AF9 oncogene, and a new Tet-on conditional shRNA expression system we have identified Myb as critical mediator of addiction to MLL-AF9. Suppression of Myb in established AML in vivo terminates aberrant self-renewal and triggers a terminal myeloid differentiation program that precisely phenocopies the effects of suppressing MLL-AF9. Remarkably, suppressing Myb effectively eradicates aggressive and chemotherapy resistant AML. To further investigate Myb dependent transcriptional programs involved in mediating aberrant self-renewal in leukemia, we globally surveyed gene expression changes following acute shRNA-induced suppression of Myb in an established Tet-on competent model of MLL-AF9;NrasG12D-induced AML. To enable regulatable suppression of Myb in AML, we retrovirally transduced established Tet-on competent MLL-AF9;NrasG12D induced AML cells with TRMPV-Neo vectors (Zuber et al., Nature Biotech, 2010) harboring shRNAs targeting Myb (shMyb.2572 and shMyb.2652), a control shRNA targeting Renilla Luciferase (shRen.713), or an empty miR30 cassette of the recipient cloning vector (Rec). Following drug selection, shRNA expression was induced by doxycycline treatment and total RNA was isolated from sorted shRNA expressing (Venus+/dsRed+) leukemia cells after 3 days of dox treatment, and subjected to Affymetrix microarray expression analysis. Expression profiles following expression of two independent Myb shRNAs were compared to those observed after induction in shRen.713- and Rec-expressing control samples (each in 3 biological replicates).