The bases of the nucleic acids of some bacterial and animal viruses: the occurrence of 5-hydroxymethylcytosine

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Abstract
The deoxyribonucleic acids of bacteriophages T2, T4, and T6 of Escherichia coli contain no cytosine. Instead, they contain a hitherto unrecognized pyrimidine which was isolated in crystalline form and found to be identical with synthetic 5- hydroxy-methylcytosine. The u.-v. absorption characteristics of 5-hydroxy-methylcytosine are descr., and those of its deamination product, 5-hydroxymethyluracil, partially descr. 5-Hydroxymethylcytosine is lost during hydrolysis of deoxyribonucleic acid with concentrated perchloric acid at 100[degree], but can be recovered almost quantitatively after hydrolysis with formic acid at 175[degree], provided that a sufficient volume is used. Yields of other bases, especially guanine, are also somewhat affected by the proportion of formic acid used. The quantitative purine and pyrimidine composition of deoxyribonucleic acid from phages T2, T4 and T6, leach in r and r+ mutants, was detd., and no differences could be detected among these viruses. The molar ratios adenine/ thymine and guanine/5-hydroxymethylcyto-sine are close to unity and the ratio (adenine+thymine)/ (guanine+ 5-hydroxymethylcytosine) is 1:8. No 5-hydroxymethylcytosine could be detected in any of the following materials: dried cells of Escherichia coli, ox-spleen deoxyribonucleic acid, phages T5 and T7, an insect polyhedral virus, vaccinia virus and meningo-pneumonitis virus. Quantitative analyses of deoxyribonucleic acid bases from phage T5 and from vaccinia virus are reported. The possible significance of 5-hydroxymethylcytosine, which may be a component peculiar to certain viruses, is discussed in relation to the metabolism of pyrimidine bases and of nucleic acids during virus infection.