OLIGONUCLEOTIDE PHOTOPRODUCTS FORMED BY PHOTOLYSIS OF POLYRIBOBROMOURIDYLIC ACID

Abstract— Polyribobromouridylic acid was irradiated with 313 nm light at an exposure of ˜ 190 pE/cm*. Oligonucleotides found after RNase hydrolysis of the photolysed poly-rBrU were isolated by DEAE-cellulose chromatography and partially characterized. The dmucleo-tide fraction, found in highest amounts, was not susceptible to hydrolysis by KOH or snake venom phosphodiesterase and may contain a coupled photoproduct. The properties of the dinucleotide were not those of a molecule containing a cyclobutane-type dimer, but were compatible with the properties of a coupled product similar to 5–5'-diuracil. The trinucleotide fraction probably consisted of more than one component. One component may contain a dimeric photoproduct. The tetranucleotide material was sensitive to cleavage into fragments by KOH, and could consist of adjacent photoproducts of the types found in the di- and trinucleotide fractions. The photoproducts formed over a range of lower doses of light were found to have properties similar to those found at high doses.