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Processing and termination of RNA polymerase I transcripts
Author(s) -
Reeder Ronald H.,
Labhart Paul,
McStay Brian
Publication year - 1987
Publication title -
bioessays
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.175
H-Index - 184
eISSN - 1521-1878
pISSN - 0265-9247
DOI - 10.1002/bies.950060304
Subject(s) - transcription (linguistics) , rna polymerase ii , biology , internal transcribed spacer , rna polymerase i , rna polymerase , polymerase , gene , genetics , ribosomal rna , rna polymerase ii holoenzyme , rna polymerase iii , rna , transcription factor ii d , gene expression , microbiology and biotechnology , promoter , philosophy , linguistics
Electron micrographs of active ribosomal genes from many species show a similar picture in which gene regions covered with nascent transcripts alternate with apparently non‐transcribed spacers. Since the gradients of visible nascent transcripts stop near the 3 ′ end of the 28 S sequence it has often been assumed that transcription by RNA polymerase I also terminates at that point. Recent biochemical studies have shown however, that transcription continues far beyond the 3 ′ end of the 28 S and in some species continues across the entire spacer. In this article we review the evidence for spacer transcription in Xenopus , mouse and Drosophila and discuss possible reasons for its invisibility in the electron microscope.