Edward N. Trifonov

A representative set of 168 eukaryotic POL II promoters has been compiled from the EMBL library and subjected to computer signal search analysis. Application of this technique to E. coli promoters as a control ensemble revealed the well known consensus sequences at -35 and -10 which indicates that the methods are adequate to approach problems of this kind. The results obtained from the eukaryotic promoter set can be summarized as follows: Common sequence features are confined to a region between -50 and +10 relative to the transcriptional initiation site. The only well conserved consensus sequence is TATAAA, centered at -28. A weak motif, CA followed preferentially by pyrimidines, surrounds the cap-site. Two pentanucleotides which have been shown by experiments to stimulate transcription of certain genes, GGGCG and CCAAT, are moderately over-represented in the upstream region (between -129 and -50). However, they occur at highly variable distances from the initiation site.

A priori considerations and the concept of the sequence-dependent local curving of the DNA axis. Experimental evidence: electric dichroism (relaxation time measurements); anomalous electrophoretic mobility and gel-filtration of some restriction fragments of DNA; one-sided binding of the nucleosomal DNA to the mica surface. Theoretical predictions concerning the nucleotide sequences of the curved DNA. Discovery of the dinucleotide periodicity in the chromatin DNA. The sequence periodicity as a tool for mapping of the nucleosomes along the sequences. Preferential binding of the histone octamers to the curved pieces of DNA--sequence analysis predictions and comparison with experiments: Theoretical and experimental estimates of the tilt and roll angles for different combinations of the neighboring base-pairs. Inherent sequence-dependent curvature and apparent persistence length of DNA.

Analysis of the vocabulary of 123 tabulated definitions of life reveals nine groups of defining terms (definientia) of which the groups (self-)reproduction and evolution (variation) appear as the minimal set for a concise and inclusive definition: Life is self-reproduction with variations.

The concept of "words" in continuous languages devoid of blanks is introduced and an operational definition of words given. With this novel concept nucleotide sequences become object for linguistic analysis. The typical word size of the nucleotide language is found to be 3 to 5 (tri- to pentamers). Different genomes have distinct vocabularies. Comparison of these vocabularies can serve as a basis for revealing functional and evolutionary relatedness of sequences.