E. Ford et N. Hernandez, CHARACTERIZATION OF A TRIMERIC COMPLEX CONTAINING OCT-1, SNAP(C), ANDDNA, The Journal of biological chemistry, 272(25), 1997, pp. 16048-16055
The human small nuclear (su) RNA promoters contain a proximal sequence
element (PSE), which recruits the basal transcription factor SNAP(c),
and a distal sequence element characterized by an octamer sequence, w
hich recruits the POU domain transcription factor Oct-1, The Oct-1 POU
domain and SNAP(c) bind cooperatively to probes containing a PSE and
an octamer sequence, and this effect contributes to efficient transcri
ption in vitro. In vivo, however, Oct-1 regions outside of the POU dom
ain can activate snRNA gene transcription. Here, we have examined whet
her the role of these regions is to contribute to cooperative binding
with SNAP(c). We find that they indeed improve cooperative binding, bu
t most of the effect is nevertheless mediated by just the POU domain,
This suggests that Oct-1 activates transcription of snRNA genes In at
least two steps, recruitment of SNAP(c) mediated primarily by the POU
domain, and a later step mediated by regions outside of the POU domain
, We also show that a PSE-binding complex observed in nuclear extracts
consists of Oct-1 and SNAP(c). Although Oct-1 cannot bind effectively
to the PSE probe on its own, in the complex it contacts DNA, Thus, in
a nuclear extract, SNAP(c) can recruit Oct-1 to a probe to which Oct-
1 cannot bind on its own.