Messenger RNA encoding basic chromosomal proteins of mouse testis

Abstract

Considerable knowledge has accumulated concerning histones and other basic chromosomal proteins which appear in mammalian male germ cells during spermatogenesis. The best characterized of these proteins are testis protein (TP) and protamine. Both are small and highly basic, TP being present in early spermatids while two molecular species of mouse protamine may be detected in spermatids in the later stages of differentiation and in sperm. The amino acid sequence of TP from rat and of a single species of protamine from bull have been reported. In contrast to this detailed information related to protein structure, relatively little is known of the mechanisms involved in synthesis of the proteins or of the controls which regulate their synthesis during spermatogenesis. In the study reported here, messenger RNA (mRNA) from mouse testis was examined for its ability to act as a template for in vitro synthesis of TP and protamine. Three polyacrylamide gel electrophoresis systems were developed to distinguish TP and the two species of mouse protamine among in vitro translation products synthesized by a cell-free wheat germ extract. A 6 S RNA encoding TP was identified by translation of sucrose gradient fractions. RNA encoding TP was also found among the testis RNAs which were bound to oligo(dT)-cellulose during affinity chromatography. These physical properties and apparent abundance of this TP mRNA suggest that it may be a useful probe for further studies of RNA metabolism and gene regulation. In no case was an in vitro translation product comigrating with the two protamine species observed, suggesting the possibility that protamine may be synthesized as a precursor and later processed to the species which are found in sperm.