title: Regulation of ribosomal RNA transcription during differentiation of Acanthamoeba castellanii: a review.
abstract: During the cellular differentiation induced by starvation of Acanthamoeba castellanii, the expression of a number of genes is regulated. Evidence is reviewed that at least one of these, the precursor ribosomal RNA transcription unit, is regulated at the level of transcription. The structure of the rRNA transcription unit and of the RNA polymerases responsible for transcription in Acanthamoeba are reviewed. Utilizing an in vitro transcription system constructed from these components, preliminary evidence has been obtained that pre-rRNA gene expression is regulated by a modification of RNA polymerase I that affects the enzyme's ability to participate efficiently in the initiation of transcription. These results are reviewed in relation to other known mechanisms of transcriptional regulation in eukaryotes.
mesh_terms: D000656:Amoeba / Q000166:cytology / Q000235:genetics*; D000818:Animals; D003001:Cloning, Molecular; D005786:Gene Expression Regulation; D009694:Nucleic Acid Precursors / Q000235:genetics; D012315:RNA Caps / Q000378:metabolism; D012318:RNA Polymerase I / Q000378:metabolism; D012319:RNA Polymerase II / Q000378:metabolism; D012320:RNA Polymerase III / Q000378:metabolism; D012335:RNA, Ribosomal / Q000235:genetics*; D012270:Ribosomes / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D009694:Nucleic Acid Precursors; D012315:RNA Caps; D012335:RNA, Ribosomal; D014157:Transcription Factors; D012319:RNA Polymerase II; D012318:RNA Polymerase I; D012320:RNA Polymerase III