Nucleic Acids Research, Vol 26, Issue 3 703-709, Copyright © 1998 by Oxford University Press
RF Ryan and MK Darby
Transcription factor IIIA (TFIIIA) and p43 zinc finger protein form
distinct complexes with 5S ribosomal RNA in Xenopus oocytes. Additionally,
TFIIIA binds the internal promoter of the 5S RNA gene and supports assembly
of a transcription initiation complex. Both proteins have nine tandemly
repeated zinc fingers with almost identical linker lengths between
corresponding fingers, yet p43 has no detectable affinity for the 5S RNA
gene. TFIIIA zinc fingers 1-3 are connected by highly conserved linkers,
first identified in the Drosophila protein Kruppel, that are found in many
DNA binding zinc finger proteins. To understand the role of these linkers
in RNA and DNA binding we exchanged three TFIIIA linker amino acids with
the equivalent amino acids from p43. The major effect of linker
substitution is a 50-fold reduction in DNA specificity, concomitant with an
8-fold reduction in affinity. N-Terminal zinc fingers from either TFIIIA or
p43 bind to multiple specific sites on 5S RNA that are resistant to
competition by tRNA or poly(rA). This mode of RNA binding is unaffected by
linker substitution. These data suggest that zinc finger linkers
significantly facilitate the specificity of DNA binding.
ARTICLES
The role of zinc finger linkers in p43 and TFIIIA binding to 5S rRNA and DNA
Department of Microbiology and Immunology, Kimmel Cancer Institute, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA.
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