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Journal of Virology, January 1999, p. 772-777, Vol. 73, No. 1
Department of Molecular Microbiology and
Immunology1 and
Howard Hughes Medical
Institute,2 University of Southern California
School of Medicine, Los Angeles, California 90033-1054
Received 29 April 1998/Accepted 25 September 1998
A cellular protein, previously described as p55, binds specifically
to the plus strand of the mouse hepatitis virus (MHV) leader RNA. We
have purified this protein and determined by partial peptide sequencing
that it is polypyrimidine tract-binding protein (PTB) (also known as
heterogeneous nuclear ribonucleoprotein [hnRNP] I), a nuclear protein
which shuttles between the nucleus and cytoplasm. PTB plays a role in
the regulation of alternative splicing of pre-mRNAs in normal cells and
translation of several viruses. By UV cross-linking and
immunoprecipitation studies using cellular extracts and a recombinant
PTB, we have established that PTB binds to the MHV plus-strand leader
RNA specifically. Deletion analyses of the leader RNA mapped the
PTB-binding site to the UCUAA pentanucleotide repeats. Using a
defective-interfering RNA reporter system, we have further shown that
the PTB-binding site in the leader RNA is critical for MHV RNA
synthesis. This and our previous study (H.-P. Li, X. Zhang, R. Duncan,
L. Comai, and M. M. C. Lai, Proc. Natl. Acad. Sci. USA
94:9544-9549, 1997) combined thus show that two cellular hnRNPs, PTB
and hnRNP A1, bind to the transcription-regulatory sequences of MHV RNA
and may participate in its transcription.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Polypyrimidine Tract-Binding Protein Binds to the
Leader RNA of Mouse Hepatitis Virus and Serves as a Regulator of
Viral Transcription
*
Corresponding author. Mailing address: Howard Hughes
Medical Institute, Department of Molecular Microbiology and Immunology, University of Southern California School of Medicine, 2011 Zonal Ave.,
HMR-401, Los Angeles, CA 90033-1054. Phone: (323) 442-1748. Fax: (323)
442-9555. E-mail: michlai{at}hsc.usc.edu.
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