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Journal of Virology, October 2000, p. 8930-8937, Vol. 74, No. 19
Departments of Biochemistry and
Biophysics1 and
Entomology,2 Texas A&M University,
College Station, Texas 77843-2128
Received 13 March 2000/Accepted 30 June 2000
Baculovirus late RNAs are transcribed by a four-subunit RNA
polymerase that is virus encoded. The late viral mRNAs are capped and
polyadenylated, and we have previously shown that capping is mediated
by the LEF-4 subunit of baculovirus RNA polymerase. Here we report
studies undertaken to determine the mechanism of 3'-end formation. A
globin cleavage/polyadenylation signal, which was previously shown to
direct 3'-end formation of viral RNAs in vivo, was cloned into a
baculovirus transcription template. In vitro assays with purified
baculovirus RNA polymerase revealed that 3' ends were formed not by a
cleavage mechanism but rather by termination after transcription of a
T-rich region of the globin sequence. Terminated RNAs were released
from ternary complexes and were subsequently polyadenylated. Mutational
analyses indicated that the T-rich sequence was essential for
termination and polyadenylation, but the poly(A) signal and the GT-rich
region of the globin polyadenylation/cleavage signal were not required.
Termination was not dependent on ATP hydrolysis, indicating a slippage mechanism.
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Copyright © 2000, American Society for Microbiology. All rights reserved.
3'-End Formation of Baculovirus Late RNAs
*
Corresponding author. Mailing address: Department of
Biochemistry, Texas A&M University, 2128 TAMUS, College Station, TX
77843-2128. Phone: (409) 845-7556. Fax: (409) 845-9274. E-mail:
Iguarino{at}tamu.edu.
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