Practice question

Animal cells possess three canonical nucleus-encoded multisubunit DNA-dependent RNA polymerases sharing five small subunits but possessing distinct large subunits conferring functional specialization and promoter specificity. RNA polymerase I in nucleolus transcribes 45S pre-rRNA for 18S, 5.8S, 28S ribosomal RNAs. RNA polymerase II in nucleoplasm synthesizes all protein-coding pre-mRNAs, most small nuclear RNAs, microRNAs, and long noncoding RNAs. RNA polymerase III makes short stable RNAs including transfer RNAs, 5S rRNA, U6 snRNA. Plants additionally possess polymerases IV and V devoted to siRNA-directed epigenetic silencing.