A fast method for the determination of 5' terminal dinucleotides of DNA fragments

Mapping of deoxydi- and trinucleotides liberated by the action of endonucleases from the silkworm and Aspergillis oryzae

Both silkworm nuclease and nuclease O of Aspergillus oryzae mycelia hydrolyse DNA endolytically to di- and trinucleotides terminating in 5'-phosphate. These oligonucleotides were fractionated first be DEAE-cellulose chromatography with 7 M urea into the respective isoplithic groups and then analysed for the composition and isomerism: each group was labeled 5'-terminally by the [gamma-32P]ATP-polynucleotide kinase reaction and then electrophoresed monodimensionally for the dinucleotides and two-dimensionally for the di- and trinucleotides mixtures, respectively, followed by elution and digestion with snake venom exonuclease. Both nucleases gave rather similar simple maps in which all sixteen dinucleotides and almost all the possible trinucleotides were identified, indicating their random mode of actions.

Preparation and specificity of endonuclease IV induced by bacteriophage T4

Bacteriophage-T4-induced endonuclease IV suitable for DNA sequence analysis has been prepared by a modified and easily reproducible method. The specificity of T4-induced endonuclease IV has been investigated in order to verify whether this enzyme exhibits a single nucleotide recognition or a short sequence recognition. The 5'-terminal dinucleotides and 3'-terminal nucleotides of oligonucleotides released by T4-induced endonuclease IV from three single-stranded DNAs (from bacteriophages phiX174, fd, M 13) have been analysed. In different DNAs, 74-82% of the 5'-terminal dinucleotides end in 5'-deoxycytidylic acid; small but significant levels of several dinucleotides ending in 5'-deoxyadenylic acid, 5'-thymidylic acid and 5'-deoxyguanylic acid are also found. As far as 3'-terminal nucleotides are concerned all nucleotides are present with a large predominance of thymidylic acid. It is concluded that T4-induced endonuclease IV recognizes short nucleotide sequences like all other DNases investigated so far. The spectrum of such sequences is, however, very narrow.