Imboden M A, Matthews J L, Lofquist A K, Paule M R
Department of Biochemistry, Colorado State University, Fort Collins 80523.
J Biol Chem. 1992 Dec 5;267(34):24601-10.
A nuclear extract from Acanthamoeba castellanii which contains all of the components necessary for specific transcription of a 5 S RNA gene was separated into fractions required for specific transcription initiation and an additional fraction needed in the reconstituted system to produce the 3' end characteristic of mature 5 S RNA. The latter fraction contained a novel processing activity characterized by an exonuclease specific for highly structured RNAs, including 5 S RNA. An intact helical stem formed between the 5' and 3' ends of the 5 S RNA precursor determines the 3' nucleotide. In addition, the presence of ATP is required for specific processing. However, the possibility has not been ruled out that ATP inhibits a nonspecific ribonuclease in the extract since processing proceeds into the helical stem in its absence.
