Histone synthesis during spermiogenesis in the grasshopper Chortophaga viridifasdata was studied using autoradiographic and cytochemical methods. It was found that meiosis is followed by a cessation of RNA synthesis, an elimination of RNA from the nucleus, and, during the cytoplasmic sloughing accompanying the initial cytoplasmic elongation, a loss of most of the RNA from the cell. The initial phase of cell elongation results in a long spermatid headed by a spherical RNA-less nucleus bounded by a thin RNA-containing layer of cytoplasm. Subsequent nuclear elongation is accompanied by a replacement of the typical histones by others rich in arginine. This replacement is the result of synthesis of new protein. Incorporation of arginine is first seen to occur in the thin cytoplasmic layer surrounding the nucleus. This layer was shown by staining and electron microscopy to contain aggregations of ribosome-like particles. These observations support the conclusion that the histone is synthesized in association with the RNA granules in the cytoplasm, then migrates into the nucleus where it combines with the DNA.
A comparison of the times necessary to incorporate tritium-labeled lysine and arginine into histones and tritium-labeled thymidine into DNA indicates that the periods of DNA and histone synthesis prior to division closely coincide. (The comparison was made by determining the times necessary, after pulse labeling, for cells with marked chromosomes to enter and then leave the division stages.) An additional period of chromosomal protein synthesis, of short duration, occurs late in interphase. Most of the chromosomal proteins appear either to be synthesized in the nucleus or to migrate there shortly after synthesis. Much of this protein is conserved from one division to the next. Studies of the effects of puromycin and fluorodeoxyuridine on the syntheses of DNA and histone suggest that continuation of DNA synthesis is dependent on a concurrent protein synthesis. Histone synthesis, on the other hand, can proceed at a normal rate under conditions in which DNA synthesis is inhibited.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.