Relationship between Nuclear and Cytoplasmic Ribonucleic Acid

Abstract

RECENTLY, Harris and Watts¹ reported on the incorporation of radiocarbon derived from [8-¹⁴C]-adenine into adenine and guanine bases of nuclear and cytoplasmic RNA in logarithmically growing HeLa cells. The complex nature of curves of specific activity versus time under varying experimental conditions was interpreted by these authors as primarily due to synthesis of cytoplasmic RNA in the cytoplasm from acid-soluble precursors. Similar work carried out in our laboratory led to an entirely different conclusion. Our results were consistent with a ‘partial’ precursor–product relationship, in which the nuclear RNA acted as a precursor to a major fraction of the cytoplasmic RNA (unpublished results). The arguments put forth by Harris and Watts are based on qualitative evidence. This led us to evaluate their results on a more rigorous quantitative basis. The following analysis shows them to be compatible with a precursor–product relationship between the nuclear and cytoplasmic RNA.