Template functions in the enzymic formation of polyribonucleotides. IV. Denatured DNA as template

Template properties of complementary fractions of denatured microbial deoxyribonucleic acids

DNA preparations from seven bacterial species and from E. coli phage T4, and also the complementary L and H fractions into which these DNA specimens, after denaturation, were separated by chromatography on methylated albumin-kieselguhr columns, were studied as templates in the RNA polymerase system, and the nucleotide composition of the RNA products was determined. The RNA transcripts of the separated L and H fractions were found to be faithful copies of the respective DNA fractions. This suggests "transcription analysis" as a sensitive and reliable analytical technique for the determination of the base composition of denatured DNA. The L and H fractions of T4 DNA were shown, both by temperature-absorbance profiles and by transcription analysis, to be mutually complementary. The RNA products formed with intact DNA as the template were not exact copies of the latter; their composition indicated that under our experimental conditions the "heavy" DNA strand is transcribed preferentially.

Complementary fractions of denatured DNA of coliphage T3 as templates for transcription

This paper discusses the evidence that two fractions obtained by the chromatography of denatured DNA of phage T3 on columns of methylated albumin-kieselguhr represent the complementary strands. This evidence derives from a variety of temperature-absorbance measurements and from the base composition of the RNA products synthesized by RNA polymerase under the direction of the two single-stranded DNA templates.

Studies on the chromatin of barley leaves during senescence

1. The activity of soluble ribonuclease and deoxyribonuclease first declined during senescence, but later increased during advanced stages of senescence. 2. Young leaves had very low ribonuclease or deoxyribonuclease activity associated with the chromatin, but the activity of these enzymes increased progressively during senescence until the leaves died. 3. No significant changes in the composition of chromatin from first seedling leaves of barley plants during aging (from 7 to 25 days) were noted. 4. The amount of RNA synthesized by chromatin in vitro declined as the leaf aged. However, if the loss of RNA due to chromatin-associated ribonuclease was taken into account, the RNA-synthesizing activity of chromatin from senescing (15-16-day-old) leaves appeared to be somewhat higher than that of chromatin from young (7-8-day-old) leaves. In leaves at the terminal stages of senescence (23 days old) the estimates of RNA synthesis by chromatin could not be made owing to complications created by high nuclease activities. 5. It is suggested that senescence may be triggered by a decline in some hormonal factor in leaves, and that the resulting production of chromatin-associated deoxyribonuclease and ribonuclease in increasing proportions may progressively cause increased degradation of DNA and newly synthesized RNA, so that ultimately the cellular functions are impaired and the cells die.