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Molecular and Cellular Biology, November 2000, p. 8198-8208, Vol. 20, No. 21
Department of Biology and Curriculum in
Genetics and Molecular Biology, University of North Carolina at
Chapel Hill, Chapel Hill, North Carolina 27599-3280
Received 30 May 2000/Returned for modification 11 July
2000/Accepted 1 August 2000
The Drosophila melanogaster suppressor of sable gene,
su(s), encodes a novel, 150-kDa nuclear RNA binding
protein, SU(S), that negatively regulates RNA accumulation from mutant
alleles of other genes that have transposon insertions in the 5'
transcribed region. In this study, we delineated the RNA binding domain
of SU(S) and evaluated its relevance to SU(S) function in vivo. As a
result, we have defined two arginine-rich motifs (ARM1 and ARM2) that
mediate the RNA binding activity of SU(S). ARM1 is required for in
vitro high-affinity binding of SU(S) to small RNAs that were previously
isolated by SELEX (binding site selection assay) and that contain a
common consensus sequence. ARM1 is also required for the association of
SU(S) with larval polytene chromosomes in vivo. ARM2 promotes binding
of SU(S) to SELEX RNAs that lack the consensus sequence and apparently
is neither necessary nor sufficient for the stable polytene chromosome
association of SU(S). Use of the GAL4/UAS system to drive ectopic
expression of su(s) cDNA transgenes revealed two previously
unknown properties of SU(S). First, overexpression of SU(S) is lethal.
Second, SU(S) negatively regulates expression of su(s)
intronless cDNA transgenes, and the ARMs are required for this effect.
Considering these and previous results, we propose that SU(S) binds to
the 5' region of nascent transcripts and inhibits RNA production in a
manner that can be overcome by splicing complex assembly.
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Arginine-Rich Regions Mediate the RNA Binding and
Regulatory Activities of the Protein Encoded by the
Drosophila melanogaster suppressor of sable Gene

*
Corresponding author. Mailing address: Department of
Biology, CB# 3280, UNC at Chapel Hill, Chapel Hill, NC 27599-3280. Phone: (919) 966-4989. Fax: (919) 962-1625. E-mail:
lsearles{at}emailunc.edu.
Present address: Department of Botany, North Carolina State
University, Raleigh, NC 27695.
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