T7 RNA polymerase-directed transcripts are processed in yeast and link 3' end formation to mRNA nuclear export.
We have characterized transcripts synthesized in vivo by bacteriophage T7 RNA polymerase to investigate yeast mRNA processing. T7 transcripts are not capped, consistent with capping being tightly coupled to RNA polymerase II (pol II) transcription. In contrast to higher eukaryotic non-pol II transcripts, yeast T7 transcripts are spliced as well as cleaved and polyadenylated. However, T7 and pol II transcripts are affected differently in cleavage and polyadenylation mutant strains, indicating that pol II may have a role in yeast 3' end formation. T7 transcripts with 3' ends directed by a polyadenylation signal are exported from the nucleus, and this export is dependent on the canonical cleavage and polyadenylation machinery. Importantly, transcripts with T7 terminator-directed 3' ends are unadenylated and predominantly nuclear in wild-type cells. Our results suggest that transcription by pol II is required for neither the nuclear export of an in vivo-transcribed mRNA nor for the retention of transcripts with aberrant 3' ends. Moreover, proper 3' end formation may be necessary and sufficient to promote mRNA export in yeast.
Dower
Ken
K
Howard Hughes Medical Institute, Department of Biology, Brandeis University, Waltham, Massachusetts 02454, USA.
Rosbash
Michael
M
D021581:Active Transport, Cell Nucleus; D017123:Bacteriophage T7 / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D012319:RNA Polymerase II / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012326:RNA Splicing; D012331:RNA, Fungal / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014764:Viral Proteins
D012331:RNA, Fungal; D012333:RNA, Messenger; D012367:RNA, Viral; D014764:Viral Proteins; D012319:RNA Polymerase II; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases