Tuned polymerization of the transcription factor Yan limits off-DNA sequestration to confer context-specific repression

Abstract

During development, transcriptional complexes at enhancers regulate gene expression in complex spatiotemporal patterns. To achieve robust expression without spurious activation, the affinity and specificity of transcription factor–DNA interactions must be precisely balanced. Protein–protein interactions among transcription factors are also critical, yet how their affinities impact enhancer output is not understood. The Drosophila transcription factor Yan provides a well-suited model to address this, as its function depends on the coordinated activities of two independent and essential domains: the DNA-binding ETS domain and the self-associating SAM domain. To explore how protein–protein affinity influences Yan function, we engineered mutants that increase SAM affinity over four orders of magnitude. This produced a dramatic subcellular redistribution of Yan into punctate structures, reduced repressive output and compromised survival. Cell-type specification and genetic interaction defects suggest distinct requirements for polymerization in different regulatory decisions. We conclude that tuned protein–protein interactions enable the dynamic spectrum of complexes that are required for proper regulation.

Longevity is determined by ETS transcription factors in multiple tissues and diverse species

“…In the presence of FREs, FOXO is known to activate transcription [31]. We confirmed published observations for individual TFs on the reporters that contained their individual binding elements: FOXO was sufficient to activate transcription from the FREs (t-test t = 6.64, p = 3.7e-5), while, as expected [23,26,28], AOP ACT did not impact expression from EBMs (t-test t = -0.66, p = 0.26).…”

“…Whilst interactions with FOXO appear to account for some of the transcriptional outputs of AOP, 80% of AOP-bound genomic sites are not bound by FOXO in vivo [4]. Since AOP alone is insufficient to regulate transcription when brought onto a promoter (Fig 2A and references[21,23,26,28]), interactions with other transcriptional activators must account for the full breadth of Aop 's physiological and transcriptomic effects. Pnt is one such transcriptional activator.…”

“…Aop is one such repressor in Drosophila . Aop and its human orthologue Tel are thought to repress transcription by competing with activators for binding sites[21,23], recruiting co-repressors[22,24,25], and forming homo-oligomers that limit activator access to euchromatin[26–30]. Consequently, Aop 's role in physiology must be explored in the context of its interactions with additional TFs, especially activators.…”

Sticky, Adaptable, and Many‐sided: SAM protein versatility in normal and pathological hematopoietic states

“…[ 78 ] In Hope et al., researchers created a “SuperYan” SAM that increased its stickiness. [ 79 ] This study revealed that higher affinity SAM interactions caused protein aggregates to form and sequester into ectopic cellular compartments, abolishing normal function. Striking, they reveal that SAM mutations can cause proteins to be too sticky to function, highlighting how changes in SAM affinities can wreak havoc on normal cellular activities.…”