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Mol. Cell. Biol., Mar 1996, 1275-1281, Vol 16, No. 3
JM Li, RP Haberman and WF Marzluff
The proximal sequence element (PSE) for the sea urchin U6 small nuclear RNA
gene has been defined. The most critical nucleotides for expression,
located 61 to 64 nucleotides (nt) from the transcription start site, are 4
nt, AACT, at the 5' end of the PSE. Two nucleotide mutations in this region
abolish transcription of the sea urchin U6 gene in vitro. The same two
nucleotide mutations greatly reduce the binding of specific factors
detected by an electrophoretic mobility shift assay. There is also a
conserved AC dinucleotide 57 nt from the start site of the sea urchin U1
and U2 PSEs. The sea urchin U1 and U2 PSEs were substituted for the sea
urchin U6 PSE, with the conserved AC sequences aligned with those of the U6
PSE. Both of these genes were expressed at levels higher than those
observed with the wild-type U6 gene. Similar complexes are formed on the U1
and U2 PSEs, and formation of the complexes is inhibited efficiently by the
U6 PSE. In addition, the E-box sequence present upstream of the PSE
enhances U6 transcription from both the U1 and U2 PSEs. Finally, depletion
of a nuclear extract with a DNA affinity column containing the U6 PSE
sequence reduces expression of the U6 genes driven by the U6, U1, or U2 PSE
but does not affect expression of the 5S rRNA gene. These data support the
possibility that the same factor(s) interacts with the PSE sequences of the
U1, U2, and U6 small nuclear RNA genes expressed in early sea urchin
embryogenesis.
Copyright © 1996, American Society for Microbiology
Common factors direct transcription through the proximal sequence elements (PSEs) of the embryonic sea urchin U1, U2, and U6 genes despite minimal similarity among the PSEs
Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill 27599, USA.
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