Daxx Wrestles with Sumoylated Proteins

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Daxx Wrestles with Sumoylated Proteins
Daxx binds to SUMO-modified
factors via its SUMO-interacting motif
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Dr. Hsiu-Ming Shihs lab focused on the role of
Daxx, a novel transcriptional cofactor, in past
few years. The studies revealed that Daxx can
interact with several SUMO-modified transcription
factors. More recently, they defined a
SUMO-interacting motif (SIM) within Daxx protein
involved in SUMO binding and further demonstrated
that Daxx controls many SUMO-modified factors via
SIM. Interestingly, Daxx also interacts with
SUMO-modified PML and target to a special domain
in the nucleus by SIM. It was also revealed that
a chemical arsenic trioxide can attenuate the
Daxx-mediated gene repression. The molecular
mechanism for such regulation is that arsenic
trioxide can trigger a significant amount of PML
protein modified by SUMO and the resulting
SUMO-modified PML proteins can compete with the
SUMO-modified transcription factors for Daxx
binding and relocate the distribution of Daxx
protein to a special nuclear compartment
(Figure). These findings further provide
mechanistic insights into Daxx in SUMO-dependent
transcriptional control and subnuclear
compartmentalization. These studies have
substantially been appreciated internationally
and published in a high impact journal called
Molecular Cell on Nov.3, 2006. These findings
provide the first paradigm in SUMO field that a
transcriptional corepressor binds and regulates
sumoylated transcription factors via its SIM,
which has been high-lighted by a preview paper
(Developmental Cell 2006, 11 p596-597) and a
review paper (Current Opinion in Cell Biology
2007, 19 350-355).