R. Babb et al., OCA-B IS A FUNCTIONAL ANALOG OF VP16 BUT TARGETS A SEPARATE SURFACE OF THE OCT-1 POU DOMAIN, Molecular and cellular biology, 17(12), 1997, pp. 7295-7305
OCA-B is a B-cell-specific coregulator of the broadly expressed POU do
main transcription factor Oct-1, OCA-B associates with the Oct-1 POU d
omain, a bipartite DNA-binding structure containing a POU-specific (PO
US) domain joined by a flexible linker to a POU homeodomain (POUH), He
re, we show that OCA-B alters the activity of Oct-1 in two ways, It pr
ovides a transcriptional activation domain which, unlike Oct-1, activa
tes an mRNA-type promoter effectively, and it stabilizes Oct-1 on the
Oct-1-responsive octamer sequence ATGCAAAT, These properties of OCA-B
parallel those displayed by the herpes simplex virus Oct-1 coregulator
VP16, OCA-B, however, interacts with a different surface of the DNA-b
ound Oct-1 POU domain, interacting with both the POUS and POUH domains
and the center of the ATGCAAAT octamer sequence. The OCA-B and VP16 i
nteractions with the Oct-1 POU domain are sufficiently different to pe
rmit OCA-B and VP16 to bind the Oct-1 POU domain simultaneously, These
results emphasize the structural versatility of the Oct-1 POU domain
in its interaction with coregulators.