Summary of:  "Activator RNA Exchange during Interphase Chromatin Reprogramming".

1. Calf thymus lymphocyte nuclei were isolated and incubated with uridine-2-¹⁴C-triphosphate to label newly synthesized RNA.

2. Newly synthesized RNA was confined to the extended 10 nm microfibril portion (euchromatin) of the cell nucleus.

3. Condensed masses of heterochromatin did not contain newly synthesized RNA.

4. Nuclear fractionation resulted in the collection of isolated euchromatin and isolated heterochromatin fractions from the same nuclear sample.

5. The isolated euchromatin fraction remained active for RNA synthesis, while the isolated heterochromatin fraction remained inactive after isolation.

6. Parallel incubations of isolated euchromatin and isolated heterochromatin were employed to assay nuclear macromolecules for activator or repressor activity.

7. Addition of calf thymus total nuclear histones resulted in repression of  RNA synthesis within the isolated active euchromatin fraction.

8. Addition of calf thymus total nuclear RNA resulted in activation of RNA synthesis within the isolated repressed heterochromatin fraction, but had no additional effect on the isolated already-active euchromatin fraction.

9. Calf thymus total cytoplasmic RNA, calf thymus nuclear ribosomal RNA, yeast total RNA, and E. coli total RNA were less effective as activators of RNA synthesis within isolated heterochromatin.

10. Addition of yeast total RNA at low doses actually decreased RNA synthesis within isolated calf thymus already-active euchromatin, and at higher doses only returned RNA synthesis to its original baseline.

11. It is concluded that exogenous yeast total RNA competes with in-situ calf thymus euchromatin RNA in activating or maintaining  RNA synthesis within the isolated euchromatin fraction assay for activation of DNA transcription.

12. A simple model envisions direct competition between endogenous and exogenous activator RNA for a common DNA binding site within active euchromatin.

13. Such a chromatin DNA binding site lies within a zone of histone displacement.
 
 

Return to: "Activator RNA Exchange during Interphase Chromatin Reprogramming".

Return to:  "Subjects of Study in Cell and Chromatin Reprogramming":

Return to:  "RNA-Induced Chromatin Remodeling and DNA Melting during Selective Gene Transcription".
 

Further Topics in:  Euchromatin,  active DNA, and  RNA  ribo-regulators:

Links to Euchromatin Activator RNA Reviews:
Links to Euchromatin Activator RNA Research:
Links to Ultrastructural Probes of DNase I-Sensitive Sites:
Links to RNA as a Therapeutic Agent:
Links to Hodgkin Lymphoma Immuno-Pathology:
Links to Activated T-Lymphocyte Immunotherapy:
Links to Medical Systems Biology:

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

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