Related base sequences in the DNA of simple and complex organisms. IV. Evolutionary divergence of base sequence in mouse L-cell cytoplasmic and nucleus-restricted RNA

Nuclear and cytoplasmic RNAs of mouse L-cells were compared for base sequence relatedness between and within them. The relationship of each of these RNAs to the DNA of other rodents and the rabbit was determined. RNA restricted to the mouse L-cell nucleus is unrelated in base sequence to cytoplasmic RNA. There is less diversity of base sequence within the gene families transcribing nucleus-restricted RNA than within those transcribing cytoplasmic RNA, suggesting more recent evolutionary origin. The gene families which code for mouse L-cell unique nuclear RNA are far more divergent from those of other rodents than are cytoplasmic RNA gene families. They are unrelated in base sequence to any gene families in rabbit DNA, suggesting that these gene families evolved after the separation of the ancestors of the orders Rodentia and Lagomorpha. The known characteristics of the RNA restricted to the nucleus in eukaryotic cells are summarized.This investigation was supported by U.S. Public Health Service Training Grant GM 00182 and Research Grant GM 12449 from the Institute of General Medical Sciences.