A SUMO-regulated activation function controls synergy of c-Myb through a repressor–activator switch leading to differential p300 recruitment

Abstract

Synergy between transcription factors operating together on complex promoters is a key aspect of gene activation. The ability of specific factors to synergize is restricted by sumoylation (synergy control, SC). Focusing on the haematopoietic transcription factor c-Myb, we found evidence for a strong SC linked to SUMO-conjugation in its negative regulatory domain (NRD), while AMV v-Myb has escaped this control. Mechanistic studies revealed a SUMO-dependent switch in the function of NRD. When NRD is sumoylated, the activity of c-Myb is reduced. When sumoylation is abolished, NRD switches into being activating, providing the factor with a second activation function (AF). Thus, c-Myb harbours two AFs, one that is constitutively active and one in the NRD being SUMO-regulated (SRAF). This double AF augments c-Myb synergy at compound natural promoters. A similar SUMO-dependent switch was observed in the regulatory domains of Sp3 and p53. We show that the change in synergy behaviour correlates with a SUMO-dependent differential recruitment of p300 and a corresponding local change in histone H3 and H4 acetylation. We therefore propose a general model for SUMO-mediated SC, where SUMO controls synergy by determining the number and strength of AFs associated with a promoter leading to differential chromatin signatures.

Activation of the LMO2 oncogene through a somatically acquired neomorphic promoter in T-cell acute lymphoblastic leukemia

“…Interestingly, 2 clones (4H12 and 6D4) that increased the distance between the native and the mutant MYB sites resulted in a marked reduction in LMO2 expression, supporting the hypothesis that MYB binding is augmented when additional motifs are orientated on the same side of the DNA helix. 23 This was further validated by the lack of reduction in LMO2 expression in a clone (5F10) in which the sequence between the 2 MYB sites was altered but the spacing distance was unchanged.…”

Characterization of the non-coding control region of polyomavirus KI isolated from nasopharyngeal samples from patients with respiratory symptoms or infection and from blood from healthy blood donors in Norway

“…All mutations were verified by sequencing. The human c-Myc expression plasmid was a kind gift from Odd Stokke Gabrielsen (Molvaersmyr et al, 2010).…”

Inhibition of Myb-dependent gene expression by the sesquiterpene lactone mexicanin-I

“…17 The luciferase reporter gene pGL4-5xMRE(GG)-Myc contains five tandem copies of an Myb-binding site upstream of the human c-myc core promoter. 25 The b-galactosidase reporter gene pCMVb was from Clontech (Heidelberg, Germany). Expression vectors for v-Myb (pCDE26v-myb) and human c-Myb (pCIneo-HcM-HA) have been described.…”