An Escherichia coli endonuclease responsible for primary cleavage of in vitro transcripts of bacteriophage T4 tRNA gene cluster.

An endonuclease activity was isolated from 100,000 g supernatant fraction of Escherichia coli using in vitro primary transcripts of T4 tRNA gene cluster as assay substrates. The endonuclease cleaves the polycistronic RNA precursors into fragments containing monomeric and dimeric stable RNA sequences. The result strongly suggest that this enzyme participates in the early steps of T4 tRNA maturation pathway preceding the action of RNase P.