Transcription by RNA polymerase II during Acanthamoeba differentiation

The rates of transcription of several protein coding genes during Acanthamo eba differentiation have been examined by nuclear run-on and RNase protecti on assays. During early encystment, transcription by RNA polymerase II incr eases approximately 4-fold, whereas transcription by RNA polymerases I and III is decreased, as previously described. The rates of transcription from a wide variety of individual genes are only slightly affected during the fi rst 16 h of encystment, although profilin gene expression is markedly incre ased. The levels of mRNAs encoding TPBF, TATA binding protein, cyclin-depen dent kinase, protein disulfide isomerase, profilin, myosin II heavy chain, ubiquitin and extendin are stable during mature cyst formation, whereas mRN As encoding actin, S-adenosyl methionine synthase and tubulin are substanti ally decreased in abundance within 16 h of starvation-induced encystment. W e conclude that in contrast to the negative regulation of large rRNA and 5S rRNA synthesis during differentiation, the RNA polymerase II transcription apparatus is not negatively regulated. Control of Acanthamoeba differentia tion is likely to be mediated by positive regulation of genes necessary for cyst maturation. (C) 1998 Elsevier Science B.V. All rights reserved.