I. Barrai et al., POSSIBLE IDENTITY OF TRANSCRIPTION AND TRANSLATION SIGNALS IN EARLY VITAL SYSTEMS, Journal of theoretical biology, 169(3), 1994, pp. 289-294
The distribution of codons was analysed in three classes of eukaryote
proteins having widely different evolutionary rates: 78 histones, 40 t
ubulins, and seven fibrinogens. In this set of genes, (i) it was confi
rmed that codons which are components of known transcription signals,
like ATA, are used infrequently when a synonym is available, particula
rly in the more constrained proteins, and (ii) it was observed that th
e three codons which have an iso-accepting transfer with anticodon UAA
, UAG or UGA are also suppressed. Then, the distribution of UAA, UAG a
nd UGA trimers was studied in 498 tDNAs and 198 rDNAs. It was found th
at these trimers are weakly but significantly suppressed in tDNAs and
to a lesser extent in rDNAs. It was advanced that the present suppress
ion of ATA, which codes for Methionine in several mitochondria, and of
the TAA, TAG and TGA trimers in tDNAs, might be an indication that at
the very early stages of the evolution of translation and transcripti
on the signals for initiation and termination were shared by the two p
rocesses.