Líffræðifélag Íslands - biologia.is
Líffræðiráðstefnan 2023
Höfundar / Authors: Sigríður St. Hlynsdóttir, Pétur Orri Heiðarsson
Starfsvettvangur / Affiliations: University of Iceland
Kynnir / Presenter: Sigríður St. Hlynsdóttir
PU.1 is a pioneer transcription factor (pTF) in the hematopoietic lineage which has been implicated in various blood disorders and diseases. As a pTF, PU.1 targets and binds to condensed chromatin and initiates cell fate changes. PU.1’s N-terminal is an intrinsically disordered region (IDR) that includes the transactivation domain. The IDR is important for PU.1´s pioneer activity through a poorly understood mechanism but these regions may be important to recruit other TFs or interact with the nucleosome. Although PU.1 has been identified as a potential therapeutic target, little is known about the biochemical and biophysical properties of the protein.
We use single-molecule spectroscopy in combination with FRET to study the dynamics of IDRs. Our results show that PU.1 binds to short DNA harboring its recognition sequence with high affinity and that the binding alters the conformations of the disordered N-terminal tail. We have also identified two distinct PU.1 populations that exhibit different behaviors, with varying degrees of sensitivity to denaturing agents and salt concentrations. Furthermore, we have observed a potential dimer formation on and off DNA, with low nanomolar affinity, that affects the conformations of the IDR. By characterizing the physical principles behind PU.1’s function, we may unlock a useful tool in research of the hematopoietic system and take a step forward in understanding intrinsically disordered proteins and pioneer transcription factors.