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Molecular and Cellular Biology, April 2000, p. 2926-2932, Vol. 20, No. 8
Department of Microbiology, Microbiology and
Virology Graduate Program, School of Medicine, University of
Pennsylvania, Philadelphia, Pennsylvania 19104-6142
Received 29 October 1999/Returned for modification 24 November
1999/Accepted 10 January 2000
The structure of the highly efficient simian virus 40 late
polyadenylation signal (LPA signal) is more complex than those of most
known mammalian polyadenylation signals. It contains efficiency elements both upstream and downstream of the AAUAAA region,
and the downstream region contains three defined elements (two U-rich elements and one G-rich element) instead of the single U- or GU-rich element found in most polyadenylation signals. Since many reports have indicated that the secondary structure in RNA may play a significant role in RNA processing, we have used nuclease structure analysis techniques to determine the secondary structure of the LPA
signal. We find that the LPA signal has a functionally significant secondary structure. Much of the region upstream of AAUAAA
is sensitive to single-strand-specific nucleases. The region
downstream of AAUAAA has both double- and single-stranded
characteristics. Both U-rich elements are predominately sensitive to
the double-strand-specific nuclease RNase V1, while the
G-rich element is primarily single stranded. The U-rich element closest
to AAUAAA contains four distinct RNase
V1-sensitive regions, which we have designated structural region 1 (SR1), SR2, SR3, and SR4. Linker scanning mutants in the
downstream region were analyzed both for structure and for function by
in vitro cleavage analyses. These data show that the ability of the
downstream region, particularly SR3, to form double-stranded structures
correlates with efficient in vitro cleavage. We discuss the possibility
that secondary structure downstream of the AAUAAA may be
important for the functions of polyadenylation signals in general.
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Functionally Significant Secondary Structure of the
Simian Virus 40 Late Polyadenylation Signal
*
Corresponding author. Mailing address: 314 Biomedical
Research Building, 421 Curie Blvd., School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6142. Phone: (215) 898-3256. Fax:
(215) 573-3888. E-mail: alwine{at}mail.med.upenn.edu.
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