3'-end formation of baculovirus late RNAs.
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.
Jin
J
J
Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128, USA.
Guarino
L A
LA
D020413:3' Untranslated Regions / Q000235:genetics; D016367:Baculoviridae / Q000235:genetics*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics*; D014158:Transcription, Genetic
D020413:3' Untranslated Regions; D012367:RNA, Viral; D012321:DNA-Directed RNA Polymerases