Electrophoresis on polyacrylamide gels was found to be a powerful technique for separating the mature from the precursor forms of bacterial ribosomal nucleic acid (rRNA). The separation of the 16S rRNA from its precursor was, for all practical purposes, complete; that of the 23S rRNA from its precursor was detectable but incomplete. When mature and precursor rRNA preparations were heated to randomize secondary structure, etc., and then cooled, it was found that electrophoretic mobility differences between mature forms of rRNA and their precursors persisted. This, in conjunction with the rather large electrophoretic mobility differences between mature and precursor forms, can be taken as strong evidence for a molecular weight difference between mature rRNA and its precursor forms of RNA. With the 16S rRNA, this difference could be as large as 130,000 daltons.

Bacillus subtilis↗

PubMedDate not supplied

Mapping of PRM1 to human chromosome 16 and tight linkage of Prm-1 and Prm-2 on mouse chromosome 16.

The protamines are small, arginine-rich nuclear proteins that replace histones and transition proteins late in the haploid phase of spermatogenesis in mammals. The two mouse genes encoding protamines--Prm-1 and Prm-2--have been molecularly cloned and mapped to mouse chromosome 16 (MMU 16). A cDNA clone of mouse Prm-1 that hybridized to the corresponding human gene was used to analyze a panel of somatic cell hybrids made between human lymphoblasts and the E36 hamster cell line. The human gene, which we have designated PRM 1, was syntenic with human chromosome 16 (HSA 16) and discordant with all other human chromosomes. Linkage analysis in the mouse was accomplished using the backcross (Czech II x BALB/c Pt) x Czech II to map Prm-1 and Prm-2 to a position near the 5' terminus of MMU 16. No recombination between Prm-1 and Prm-2 was observed among 89 progeny of the Czech II x BALB/c cross or among 94 progeny of the backcross (CBA/J x BALB/cJ) x BALB/cJ, demonstrating that the two loci are separated by less than 1.6 cM on MMU 16. This tight linkage may be of functional significance, as Prm-1 and Prm-2 are among a limited number of genes known to be expressed postmeiotically in male haploid germ cells.

Animals↗

PubMedDate not supplied

Contrin, the human homologue of a germ-cell Y-box-binding protein: cloning, expression, and chromosomal localization.

Inactivation of germ-cell-specific molecules essential for the production of functional spermatozoa could lead to attractive new means for male contraception. The mouse protein MSY2 is the mammalian homologue of a class of Xenopus DNA/RNA-binding proteins needed for the transcription of testis-specific genes and for translational repression (masking) of paternal mRNAs. In this report, we describe the human homologue for MSY2, Contrin. Sequence analysis of Contrin cDNAs predicts a protein highly similar to its mouse and Xenopus germ-cell Y-box protein homologues with a cold shock domain and four basic/aromatic islands. Contrin is highly basic and is rich in the amino acids arginine and proline. It contains seven putative casein kinase 2 phosphorylation sites and three putative protein kinase C phosphorylation sites, suggesting that Contrin could be highly phosphorylated in vivo. The predicted protein sequence contains two nuclear localization signals, consistent with its predicted role of shuttling between nucleus and cytoplasm. Contrin maps to human chromosome 17p11.2-13.1. By the criteria of northern and western blotting, Contrin appears to be testis specific and distinct from other mammalian Y-box-binding proteins. We predict that inactivation of Contrin function in mammalian germ cells would prevent the formation of functional male gametes.

Adult↗

PubMedDate not supplied

Developmental expression of glutathione peroxidase, catalase, and manganese superoxide dismutase mRNAs during spermatogenesis in the mouse.

We have examined in mouse testis the steady-state levels of mRNAs encoding glutathione peroxidase (GSHPx), catalase (CAT), and superoxide dismutase 2 (SOD-2), three enzymes essential for the antioxidant protection of cells. In RNA preparations derived from prepuberal and adult testes and from isolated populations of meiotic and post-meiotic germ cells, one major GSHPx mRNA of about 0.8 kilobases (kb) and one major CAT mRNA of about 2.4 kb were detected. Three SOD-2 mRNAs of about 2.2, 1.2, and 1.0 kb were found in testis. In contrast to GSHPx and CAT, the mRNA levels of SOD-2 were higher in testis than in liver. SOD-2 mRNA levels are developmentally and translationally regulated with maximal levels of expression in early post-meiotic germ cells, whereas the levels of GSHPx and CAT mRNAs are relatively constant in both prepuberal and adult testes. These data suggest that translational regulation plays a more prominent role for SOD-2 expression than for GSHPx or CAT expression in the mammalian testis.

Animals↗

PubMedDate not supplied

Sertoli cells in culture and mRNA differential display provide a sensitive early warning assay system to detect changes induced by xenobiotics.

We have used cultured rat Sertoli cells as an "early warning system" to monitor for morphological and biochemical changes induced by two different xenobiotics-cadmium acetate and polychlorinated biphenyls (PCBs). Sertoli cells begin to round, become vacuolized, and detach from their substrate within 24 hours of culture in the presence of cadmium at concentrations of 0.5-1.0 microM. Similar results were obtained with a lower dose of cadmium (0.01 microM) after 72 hours. When Sertoli cells are cultured for 24 hours in the presence of a mixture of PCBs (3,3',4,4'-tetrachlorobiphenyl, 2,2',4,6,6'-pentachlorophenyl, and 2,2',3,3',4,5,5', 6,6'-nonachlorobiphenyl) at concentrations of 1.0-2.0 microM, they enlarge. After 72 hours, a lower dose of PCBs (0.01 microM) produces similar cellular enlargement. Despite their changes in morphology, no reduction in Sertoli cell viability was seen at any of the concentrations or time points studied for either toxicant. Using mRNA differential display, a number of novel cDNAs were detected when cells were cultured with either cadmium or the PCBs, demonstrating that changes in gene expression accompany the changes in Sertoli cell structure. We propose that Sertoli cells in culture and mRNA differential display provide a sensitive morphological and biochemical assay system to detect early direct effects of low concentrations of toxicants on mammalian Sertoli cells.

Acetates↗