Goldstein L, Wise GE, and Ko C,

Department of Molecular, Cellular and Developmental Biology
University of Colorado, Boulder, Colorado 80302

   The localization of small nuclear ribonucleic acids (snRNAs) during mitosis in Amoeba proteus was studied by high voltage (1,000 kV) electron microscope autoradiography. By suitable micromanipulations, the snRNA's, labeled with [³H]uridine, were made to be the only radioactive molecules in the cell and thus easy to follow autoradiographically.
   During interphase the snRNA label, which is almost exclusively nuclear, is distributed fairly uniformly through the nucleus with a slightly higher amount of label over chromatin than over nonchromatin areas. During prophase the snRNAs, which continue to be largely nuclear, become highly concentrated in the condensing chromosomes. At metapase, almost all of the snRNAs are cytoplasmic and essentially none are associated with the maximally condensed chromatin. Beginning in early anaphase, the snRNAs resume their association with the chromosomes, with the degree of association increasing throughout anaphase. Most of the snRNAs are back in the nuclei by telophase, but the intranuclear localization is hard to determine. We conclude that snRNAs have a great affinity for the partially condensed chromosomes of prophase and anaphase, but none for the maximally condensed chromosomes of metaphase.
   A minor amount of snRNA localizations in association with nucleoli and the nuclear envelope are also reported.
   On the basis of these findings a role of snRNAs in genetic "reprogramming" or chromosome organization is proposed. 

1. Nakatsu SL, Masek MA, Landrum S, and Frenster JH, "Activity of DNA Templates During Cell Division and Cell Differentiation", Nature vol. 248, no. 5446, pp. 334-335 (March 22, 1974).

2. Frenster JH, Nakatsu SL, and Masek MA, "Ultrastructural Probes of DNA Templates within Human Bone Marrow and Lymph Node Cells", Adv. Cell. Molec. Biol. vol. 3: pp. 1-19 (1974), ed. DuPraw EJ, New York: Academic Press.

3. Goldstein L, "Stable Nuclear RNA Returns to Post-Division Nuclei Following Release to the Cytoplasm during Mitosis", Exp. Cell Res. vol. 89, no. 2, pp. 421-425 (December, 1974).

4. Frenster JH, "Nuclear RNA Species Activate DNA Transcription Within Chromatin", FASEB Journal 13: No. 7, A1506 (April 23, 1999).

5. Frenster JH, "Yeast RNA Re-Programming of Already-Active Mammalian Chromatin", "RNA 2002", p. 592, Bethesda, MD: The RNA Society, May 28th - June 2nd, 2002.

6. Hovsepian JA, and Frenster JH, "RNA-Induced Melting of DNA during Selective Gene Transcription", Mol. Biol. Cell, vol. 13, supp. p. 239a (November, 2002).

7. Prasanth KV, Sacco-Bubulya PA, Prasanth SG, and Spector DL, “Sequential Entry of Components of Gene Expression Machinery into Daughter Nuclei”, Mol. Biol. Cell 14: 1043-1057 (March, 2003).

8. Saha S, Ansari AZ, Jarell KA, and Ptashne M, "RNA Sequences that Work as Transcriptional Activating Regions", Nucleic Acid Research, vol. 31, no. 5, pp. 1565-1570 (March 1, 2003).

9. Frenster JH, and Hovsepian JA, "Overshoot in Late Telophase for RNA Re-Programming of Mitotic Chromatin", "RNA 2003", Bethesda, MD: The RNA Society, July 1-6, 2003.