ABSTRACT
Our work and that of others defined mitosis-specific (Rad21 subfamily) and meiosis-specific (Rec8 subfamily) proteins involved in sister chromatid cohesion in several eukaryotes, including humans. Mutation of the fission yeast Schizosaccharomyces pombe rec8 gene was previously shown to confer a number of meiotic phenotypes, including strong reduction of recombination frequencies in the central region of chromosome III, absence of linear element polymerization, reduced pairing of homologous chromosomes, reduced sister chromatid cohesion, aberrant chromosome segregation, defects in spore formation, and reduced spore viability. Here we extend the description of recombination reduction to the central regions of chromosomes I and II. We show at the protein level that expression of rec8 is meiosis specific and that Rec8p localizes to approximately 100 foci per prophase nucleus. Rec8p was present in an unphosphorylated form early in meiotic prophase but was phosphorylated prior to meiosis I, as demonstrated by analysis of the mei4 mutant blocked before meiosis I. Evidence for the persistence of Rec8p beyond meiosis I was obtained by analysis of the mutant mes1 blocked before meiosis II. A human gene, which we designate hrec8, showed significant primary sequence similarity to rec8 and was mapped to chromosome 14. High mRNA expression of mouse and human rec8 genes was found only in germ line cells, specifically in testes and, interestingly, in spermatids. hrec8 was also expressed at a low level in the thymus. Sequence similarity and testis-specific expression indicate evolutionarily conserved functions of Rec8p in meiosis. Possible roles of Rec8p in the integration of different meiotic events are discussed.
Subject(s)
Cell Cycle Proteins , Chromatids/genetics , Fungal Proteins/genetics , Meiosis/genetics , Nuclear Proteins/genetics , Phosphoproteins/genetics , Recombination, Genetic/genetics , Schizosaccharomyces pombe Proteins , Amino Acid Sequence , Chromosome Mapping , Chromosomes/genetics , Chromosomes, Human, Pair 14 , Cloning, Molecular , DNA-Binding Proteins , Eukaryotic Cells , Evolution, Molecular , Fungal Proteins/metabolism , Gene Expression/genetics , Genetic Complementation Test , Germ Cells/metabolism , Humans , Immunohistochemistry , Molecular Sequence Data , Mutation/genetics , Phosphorylation , Phylogeny , RNA, Messenger/metabolism , Saccharomyces/genetics , Sequence Alignment , Sequence Analysis, DNAABSTRACT
Interlineage human-mouse hybrids were constructed by fusion of human acute undifferentiated leukaemia cells with the mouse thymoma cell line BW5147. Some of the hybrids expressed the human differentiation antigens CD4, CD7, CD33, and CD71 (transferrin receptor). Chromosome analysis revealed that the expression of the myeloid antigen CD33 is dependent on the presence of human chromosome 19, which is in agreement with the location of CD33-coding sequences on chromosome 19, as recently reported by Peiper et al. (1987). Furthermore, these hybrids allowed us to confirm the assignment of the CD4 antigen, the CD7 antigen, and the CD71 antigen to human chromosomes 12, 17 and 3, respectively.
