Kinetics of HCMV immediate early mRNA expression in stably transfected fibroblasts.
Compelling evidence supports an intimate link in time and space between eukaryotic pre-mRNA synthesis and processing and nucleocytoplasmic transport of mature mRNA. In this study, we analyzed the kinetic behavior of these processes in a quantitative manner. We used FISH and confocal scanning laser microscopy to detect transcripts produced by an inducible human cytomegalovirus immediate early (HCMV-IE) expression system. Upon induction, a large amount of pre-mRNA accumulated in nuclear foci at or near their transcription sites and, at later time, throughout the nucleoplasm. Inhibition of RNA polymerase II activity resulted in a rapid decrease in the number of transcripts in the nuclear RNA foci (half time approximately two minutes), indicating that accumulated transcripts were rapidly spliced and then released. The dispersed nucleoplasmic transcripts exited the nucleus with a half time of approximately 10 minutes. Both processes were temperature dependent, suggesting that mRNA export is an active process. RNA polymerase II activation revealed that production of mature HCMV IE mRNAs required less than five minutes. Transcripts radiated from the gene at an average speed of approximately 0.13 microm(2)/sec from this time on. Thus, it appears that these processes are tightly linked in time and space, with the splicing reaction as a rate-limiting factor.
Snaar
Sabine P
SP
Department of Molecular Cell Biology, Laboratory for Cytochemistry and Cytometry, Leiden University Medical Center, Wassenaarseweg 72, 2333 AL Leiden, The Netherlands.
Verdijk
Pauline
P
Tanke
Hans J
HJ
Dirks
Roeland W
RW
D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D003587:Cytomegalovirus / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D007700:Kinetics; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D012319:RNA Polymerase II / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012326:RNA Splicing / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000187:drug effects; D051381:Rats; D013696:Temperature; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*
D019384:Nucleic Acid Synthesis Inhibitors; D012333:RNA, Messenger; D012319:RNA Polymerase II