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Mol. Cell. Biol., Jan 1998, 420-432, Vol 18, No. 1
O Rowland and J Segall
Transcription factor IIIA (TFIIIA) binds to the internal control region of
the 5S RNA gene as the first step in the in vitro assembly of a
TFIIIB-TFIIIC-TFIIIA-DNA transcription complex. An 81-amino-acid domain
that is present between zinc fingers 8 and 9 of TFIIIA from Saccharomyces
cerevisiae is essential for the transcription factor activity of this
protein (C. A. Milne and J. Segall, J. Biol. Chem. 268:11364-11371, 1993).
We have monitored the effect of mutations within this domain on the ability
of TFIIIA to support transcription of the 5S RNA gene in vitro and to
maintain cell viability. TFIIIA with internal deletions that removed
residues 282 to 315, 316 to 334, 328 to 341, or 342 to 351 of the
81-amino-acid domain retained activity, whereas TFIIIA with a deletion of
the short leucine-rich segment 352NGLNLLLN359 at the carboxyl-terminal end
of this domain was devoid of activity. Analysis of the effects of double
and quadruple mutations in the region extending from residue 336 to 364
confirmed that hydrophobic residues in this portion of the 81-amino-acid
domain, particularly L343, L347, L354, L356, L357, and L358, and to a
lesser extent F336 and L337, contributed to the ability of TFIIIA to
promote transcription. We propose that these hydrophobic residues play a
role in mediating an interaction between TFIIIA and another component of
the transcriptional machinery. We also found that TFIIIA remained active if
either zinc finger 8 or zinc finger 9 was disrupted by mutation but that
TFIIIA containing a disruption of both zinc finger 8 and zinc finger 9 was
inactive.
Copyright © 1998, American Society for Microbiology
A hydrophobic segment within the 81-amino-acid domain of TFIIIA from Saccharomyces cerevisiae is essential for its transcription factor activity
Department of Biochemistry, University of Toronto, Ontario, Canada.
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