p23 is a highly conserved ubiquitous protein, known to have an important function as a cochaperone for the
hsp90 chaperoning system (1). Studies have revealed that
p23 is a small protein (18 to 25 kDa) with a simple
structure (2, 3). p23 does not have any structural
homology with any other known proteins (1). p23 was
first discovered as a part of the Hsp90-progesterone
receptor complex along with hsp70, p54 and p50 (1). p23
is a phosphor-protein, which is highly acidic and has an
aspartic acid-rich c-terminal domain (1). Numerous
studies have found p23 to be associated with other client
proteins like Fes tyrosine kinase (4), the heme regulated
kinase HRI (5), hsf1 transcription factor (4), aryl
hydrocarbon receptor (4), telomerase (6), and
Hepadnavirus reverse transcriptase (7). In spite of
several years of study, the exact functional significance
of p23 is still not clear (8). p23 is thought to be involved
in the adenosine triphosphatemediated hsp90 binding of
client proteins (8). Since many hsp90 client proteins are
involved in oncogenic survival signaling, a recent study
has concluded p23 to be a promising target in leukemic
apoptosis (9). Hsp90 and its co-chaperone p23 are
certainly among the emerging anti-tumor targets in
oncology.