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Molecular and Cellular Biology, June 2000, p. 4188-4198, Vol. 20, No. 12
Department of Biochemistry and
Biophysics,1 Program in Molecular
Biology and Biotechnology,4 and
Lineberger Comprehensive Cancer
Center,3 University of North Carolina,
Chapel Hill, North Carolina, and Department of Biological
Sciences, Florida State University, Tallahassee,
Florida2
Received 8 March 2000/Accepted 23 March 2000
The expression of the replication-dependent histone mRNAs is
tightly regulated during the cell cycle. As cells progress from G1 to S phase, histone mRNA levels increase 35-fold, and
they decrease again during G2 phase. Replication-dependent
histone mRNAs are the only metazoan mRNAs that lack polyadenylated
tails, ending instead in a conserved stem-loop. Much of the cell cycle regulation is posttranscriptional and is mediated by the 3' stem-loop. A 31-kDa stem-loop binding protein (SLBP) binds the 3' end of histone
mRNA. The SLBP is necessary for pre-mRNA processing and accompanies the histone mRNA to the cytoplasm, where it is a
component of the histone messenger RNP. We used synchronous CHO cells
selected by mitotic shakeoff and HeLa cells synchronized at the
G1/S or the M/G1 boundary to study the
regulation of SLBP during the cell cycle. In each system the amount of
SLBP is regulated during the cell cycle, increasing 10- to 20-fold in
the late G1 and then decreasing in the S/G2
border. SLBP mRNA levels are constant during the cell cycle. SLBP
is regulated at the level of translation as cells progress from
G1 to S phase, and the protein is rapidly degraded as they
progress into G2. Regulation of SLBP may account for the
posttranscriptional component of the cell cycle regulation of histone mRNA.
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Stem-Loop Binding Protein, the Protein That Binds the 3' End
of Histone mRNA, Is Cell Cycle Regulated by Both Translational
and Posttranslational Mechanisms

*
Corresponding author. Mailing address: Program in
Molecular Biology and Biotechnology, CB# 7100, University of North
Carolina, Chapel Hill, NC 27599. Phone: (919) 962-8920. Fax: (919)
966-6821. E-mail: marzluff{at}med.unc.edu.
On leave from Department of Surgery, St. Marianna University School
of Medicine, Kawasaki 216, Japan.
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