Electron Microscopic Analysis of Asymmetry within the Cell Nucleus of DNA Helix Openings During Human Cell Activation and Cell Differentiation

Abstract

Most of the DNA molecules within an animal cell are repressed for RNA synthesis at any one time, and those DNA molecules that are active are characteristic of the particular tissue or organ within which the cell has differentiated (1). This phenomena of differential gene transcription is thought to be the epigenetic basis for such diverse cell activities as cell differentiation organ regeneration, neoplastic transformation, immune activation, and the response to steroid hormones (2). Carcinogenic chemicals, oncogenic viruses, embryogenic RNA, immune RNA, and steroid hormones all prefer to bind to single-stranded regions within DNA molecules of the host cell (3). DNA molecules which are active in RNA synthesis display short loops of such single-stranded DNA (4), which are a necessary prerequisite for the gene de-repression characteristic of animal neoplasms (5).