John H. Frenster
Physicians' Educational Series, Atherton CA 94027-5446, USA.
Voice: +1 650 367 6483; Fax:
+1 650 364 1773;
E-mail: frenster@euchromatin.net
Protein synthesis occurs within the human cell nucleus (Iborra FJ, et al, Science 293: 1139 (2001), and Crick has suggested that DNA may serve as a direct template for protein synthesis without an intervening messenger RNA molecule (Crick F, Nature 227: 561 (1970). Protein synthesis is observed in nuclear ribosomes within intact nuclei isolated from calf thymus lymphocytes (Frenster JH, et al, Proc. Natl. Acad. Sci. USA 46: 432 (1960), and such protein synthesis requires Na+1 rather than K +1 as a univalent cation while within the nucleus, and is sensitive to pre-incubation digestion with DNase, but is resistant to pre-incubation digestion with RNase. After extraction from such isolated nuclei, nuclear ribosomes >120S have only trace amounts of DNA, and remain capable of protein synthesis in a nucleus-free system, which requires nuclear pH 5 amino-acid activating enzymes, ATP, and GTP, while CTP is mildly inhibitory (Frenster JH, et al, Biochim. Biophys. Acta, 47: 130 (1961). In this nucleus-free system, protein synthesis increases over a 90 minute incubation, is sensitive to RNase digestion but not DNase digestion, is stimulated by added DNA of various species, and is inhibited by added histones or synthetic polyanions, while DNA stimulation is antagonized by simultaneous DNase digestion. The intra-nuclear system and the nucleus-free system now permit a further characterization of nuclear translation and its direct stimulation by nuclear DNA.
Supported in part by a Research Career Development Award (CA-17857) from the National Cancer Institute, and by USPHS Research Grants from the National Cancer Institute.