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Molecular and Cellular Biology, August 1999, p. 5707-5717, Vol. 19, No. 8
Department of Biochemistry, College of
Agricultural and Life Sciences, University of Wisconsin, Madison,
Wisconsin 53706
Received 19 March 1999/Returned for modification 23 April
1999/Accepted 7 May 1999
During early development, specific mRNAs receive poly(A) in the
cytoplasm. This cytoplasmic polyadenylation reaction correlates with,
and in some cases causes, translational stimulation. Previously, it was
suggested that a factor similar to the multisubunit nuclear cleavage
and polyadenylation specificity factor (CPSF) played a role in
cytoplasmic polyadenylation. A cDNA encoding a cytoplasmic form of the
100-kDa subunit of Xenopus laevis CPSF has now been isolated. The protein product is 91% identical at the amino acid sequence level to nuclear CPSF isolated from Bos taurus
thymus. This report provides three lines of evidence that implicate the X. laevis homologue of the 100-kDa subunit of CPSF in the
cytoplasmic polyadenylation reaction. First, the protein is
predominantly localized to the cytoplasm of X. laevis
oocytes. Second, the 100-kDa subunit of X. laevis CPSF
forms a specific complex with RNAs that contain both a cytoplasmic
polyadenylation element (CPE) and the polyadenylation element
AAUAAA. Third, immunodepletion of the 100-kDa subunit of
X. laevis CPSF reduces CPE-specific polyadenylation in
vitro. Further support for a cytoplasmic form of CPSF comes from
evidence that a putative homologue of the 30-kDa subunit of nuclear
CPSF is also localized to the cytoplasm of X. laevis oocytes. Overexpression of influenza virus NS1 protein, which inhibits
nuclear polyadenylation through an interaction with the 30-kDa subunit
of nuclear CPSF, prevents cytoplasmic polyadenylation, suggesting that
the cytoplasmic X. laevis form of the 30-kDa subunit of
CPSF is involved in this reaction. Together, these results indicate
that a distinct, cytoplasmic form of CPSF is an integral component of
the cytoplasmic polyadenylation machinery.
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
The Cleavage and Polyadenylation Specificity Factor
in Xenopus laevis Oocytes Is a Cytoplasmic Factor Involved
in Regulated Polyadenylation

*
Corresponding author. Mailing address: Department of
Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, 433 Babcock Dr., Madison, WI 53706. Phone: 608-262-8007. Fax: 608-262-9108. E-mail: wickens{at}biochem.wisc.edu.
Present address: McArdle Laboratory, University of
Wisconsin
Madison, Madison, WI 53706.
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