John H. Frenster

Physicians’ Educational Series, Atherton, California 94027-5446, USA
e-mail: frenster@euchromatin.net

We have compared the effects of additions of either calf thymus RNA or yeast RNA species to either active euchromatin or to repressed heterochromatin fractions isolated from calf thymus nuclei (Proc. Natl. Acad. Sci. USA 50: 1026 (1963). Adding nuclear RNA from calf thymus proved to be the most effective method for activating DNA transcription within isolated heterochromatin, with lesser effects noted following the addition of cytoplasmic thymus RNA, E. coli RNA, or yeast RNA (Nature 206: 680-683 (1965). By contrast, isolated already-active euchromatin was resistant to further additions of thymus RNA. Yeast RNA at low doses was actually inhibitory to the basal DNA transcription activity of already-active euchromatin, and higher doses of yeast RNA induced only a partial return of DNA transcription activity.

These experiments reveal at least a two-phase dose-response effect from the addition of yeast RNA to already-active calf thymus chromatin. Low doses of yeast RNA are inhibitory to original basal activity, and higher doses of yeast RNA partially return the new activation of DNA transcription to a new lower base-line. These phenomena suggest a displacement of native in-situ calf thymus RNA activators from active calf thymus euchromatin DNA sites by low doses of yeast RNA, and a replacement by higher doses of yeast RNA at these and/or other sites, to induce a new lower base-line level of diverse RNA activators of DNA transcription within such euchromatin. These phenomena are compatible with an RNA-RNA two-component displacement and replacement system involved in the re-programming of active mammalian gene DNA sites.

Supported in part by USPHS Research Grants and a Research Career Development Award from the National Cancer Institute.

http://www.euchromatin.net/

Additional References:

1. Frenster JH, "Nuclear RNA Species Activate DNA Transcription within Chromatin".

2. Frenster JH, "Ultrastructural Probes of Active DNA Sites, and the RNA Activators of DNA".

3. Chan CL, and Gross CA, "The Anti-initial Transcribed Sequence, a Portable Sequence That Impedes Promoter Escape, Requires s⁷⁰ for Function".

4. Moreira JMA, Hörz W, and Holmberg S, "Neither Reb1p nor Poly(dA·dT) Elements Are Responsible for the Highly Specific Chromatin Organization at the ILV1 Promoter".