Abstract
Transposons are important sources of binding sites for transcription factors whose specific activation characterized the embryonic development of animals. In the evolution of eukaryotes, molecular domestication of the mobile genetic elements led to the emergence of multiple novel proteins, including the transcription factors involved in the control of cell differentiation. Transposons are abundantly present in intergenic DNA, introns and 3R-untranslated regions, specifically, near the transcription factor genes which they regulate. This promotes gene interregulation through transposon activation by the products of their expression in successive divisions of stem cells, thus representing a dynamic biological encoding of the species-specific ontogenetic regulation. This program can be implemented due to tissue- and stage-specific regulation mediated by the presence of transposons at specific genomic sites. The crucial role of domesticated transposon genes in controlling genome operation and key developmental stages provides a sound argument in favor of this assumption.