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Mol. Cell. Biol., 01 1998, 368-377, Vol 18, No. 1
MW Wong, RW Henry, B Ma, R Kobayashi, N Klages, P Matthias, M Strubin and N Hernandez
The human RNA polymerase II and III snRNA promoters have similar enhancers,
the distal sequence elements (DSEs), and similar basal promoter elements,
the proximal sequence elements (PSEs). The DSE, which contains an octamer
motif, binds broadly expressed activator Oct- 1. The PSE binds a
multiprotein complex referred to as SNAPc or PTF. On DNAs containing both
an octamer site and a PSE, Oct-1 and SNAPc bind cooperatively. SNAPc
consists of at least four stably associated subunits, SNAP43, SNAP45,
SNAP50, and SNAP190. None of the three small subunits, which have all been
cloned, can bind to the PSE on their own. Here we report the isolation of
cDNAs corresponding to the largest subunit of SNAPc, SNAP190. SNAP190
contains an unusual Myb DNA binding domain consisting of four complete
repeats (Ra to Rd) and a half repeat (Rh). A truncated protein consisting
of the last two SNAP190 Myb repeats, Rc and Rd, can bind to the PSE,
suggesting that the SNAP190 Myb domain contributes to recognition of the
PSE by the SNAP complex. SNAP190 is required for snRNA gene transcription
by both RNA polymerases II and III and interacts with SNAP45. In addition,
SNAP190 interacts with Oct-1. Together, these results suggest that the
largest subunit of the SNAP complex is involved in direct recognition of
the PSE and is a target for the Oct-1 activator. They also provide an
example of a basal transcription factor containing a Myb DNA binding
domain.
Copyright © 1998, American Society for Microbiology
The large subunit of basal transcription factor SNAPc is a Myb domain protein that interacts with Oct-1
Cold Spring Harbor Laboratory and Howard Hughes Medical Institute, New York 11724, USA.
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