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DNA Packaging (dna + packaging)
Selected AbstractsSpermatozoal RNAs: What about their functions?MICROSCOPY RESEARCH AND TECHNIQUE, Issue 8 2009Jean-Pierre Dadoune Abstract The profound architectural changes that transform spermatids into spermatozoa result in a high degree of DNA packaging within the sperm head. However, the mature sperm chromatin that harbors imprinted genes exhibits a dual nucleoprotamine/nucleohistone structure with DNase-sensitive regions, which could be implicated in the establishment of efficient epigenetic information in the developing embryo. Despite its apparent transcriptionally inert state, the sperm nucleus contains diverse RNA populations, mRNAs, antisense and miRNAs, that have been transcribed throughout spermatogenesis. There is also an endogenous reverse transcriptase that may be activated under certain circumstances. It is now commonly accepted that sperm can deliver some RNAs to the ovocyte at fertilization. This review presents potential links between male-specific genomic imprinting, chromatin organization, and the presence of diverse RNA populations within the sperm nucleus and discusses the functional significance of these RNAs in the spermatozoon itself and in the early embryo following fertilization. Some recent data are provided, supporting the view that analyzing the profile of spermatozoal RNAs could be useful for assessment of male fertility. Microsc. Res. Tech. 2009. © 2009 Wiley-Liss, Inc. [source] Specificity of staphylococcal phage and SaPI DNA packaging as revealed by integrase and terminase mutationsMOLECULAR MICROBIOLOGY, Issue 1 2009Carles Ubeda Summary SaPI1 and SaPIbov1 are chromosomal pathogenicity islands in Staphylococcus aureus that carry tst and other superantigen genes. They are induced to excise and replicate by certain phages, are efficiently encapsidated in SaPI-specific small particles composed of phage virion proteins and are transferred at very high frequencies. In this study, we have analysed three SaPI genes that are important for the phage,SaPI interaction, int (integrase) terS (phage terminase small subunit homologue) and pif (phage interference function). SaPI1 int is required for SaPI excision, replication and packaging in a donor strain, and is required for integration in a recipient. A SaPI1 int mutant, following phage induction, produces small SaPI-specific capsids which are filled with partial phage genomes. SaPIbov1 DNA is efficiently packaged into full-sized phage heads as well as into SaPI-specific small ones, whereas SaPI1 DNA is found almost exclusively in the small capsids. TerS, however, determines DNA packaging specificity but not the choice of large versus small capsids. This choice is influenced by SaPIbov1 gene 12, which prevents phage DNA packaging into small capsids, and which is also primarily responsible for interference by SaPIbov1 with phage reproduction. [source] Virus DNA translocation: progress towards a first ascent of Mount Pretty DifficultMOLECULAR MICROBIOLOGY, Issue 1 2006Nasib K. Maluf Summary Virion DNA molecules of large dsDNA viruses are highly condensed. To pack the DNA, an ATP hydrolysis-powered motor translocates the DNA into a preformed empty protein shell, the prohead. The icosahedral prohead has a special fivefold vertex, the portal vertex, where the translocation machinery acts. The portal vertex contains the portal protein, a gear-shaped dodecamer of radially disposed subunits with a central channel for DNA entry. The symmetry mismatch between the fivefold symmetry of the shell vertex and the 12-fold symmetry of the portal protein has prompted DNA packaging models in which ATP-driven portal protein rotation drives DNA translocation. In this issue of Molecular Microbiology, Baumann and colleagues test portal rotation models using bacteriophage T4. A fusion between the gp20 portal protein and the HOC external shell decoration protein is used to create a block to portal rotation. Finding that DNA packaging is unimpeded in proheads containing the fusion argues that portal rotation is not crucial to DNA translocation. The paper is a landmark for describing direct testing of the mechanism of DNA translocation. [source] Sequential model of phage PRD1 DNA delivery: active involvement of the viral membraneMOLECULAR MICROBIOLOGY, Issue 5 2002A. Marika Grahn Summary DNA translocation across the barriers of recipient cells is not well understood. Viral DNA delivery mechanisms offer an opportunity to obtain useful information in systems in which the process can be arrested to a number of stages. PRD1 is an icosahedral double-stranded (ds)DNA bacterial virus with an internal membrane. It is an atypical dsDNA phage, as any of the vertex spikes can be used for receptor recognition. In this report, we dissect the PRD1 DNA entry into a number of steps: (i) outer membrane (OM) penetration; (ii) peptidoglycan digestion; (iii) cytoplasmic membrane (CM) penetration; and (iv) DNA translocation. We present a model for PRD1 DNA entry proposing that the initial stage of entry is powered by the pressure build-up during DNA packaging. The viral protein P11 is shown to function as the first DNA delivery protein needed to penetrate the OM. We also report a DNA translocation machinery composed of at least three viral integral membrane proteins, P14, P18 and P32. [source] From structure of the complex to understanding of the biologyACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2007Michael G. Rossmann The most extensive structural information on viruses relates to apparently icosahedral virions and is based on X-ray crystallography and on cryo-electron microscopy (cryo-EM) single-particle reconstructions. Both techniques lean heavily on imposing icosahedral symmetry, thereby obscuring any deviation from the assumed symmetry. However, tailed bacteriophages have icosahedral or prolate icosahedral heads that have one obvious unique vertex where the genome can enter for DNA packaging and exit when infecting a host cell. The presence of the tail allows cryo-EM reconstructions in which the special vertex is used to orient the head in a unique manner. Some very large dsDNA icosahedral viruses also develop special vertices thought to be required for infecting host cells. Similarly, preliminary cryo-EM data for the small ssDNA canine parvovirus complexed with receptor suggests that these viruses, previously considered to be accurately icosahedral, might have some asymmetric properties that generate one preferred receptor-binding site on the viral surface. Comparisons are made between rhinoviruses that bind receptor molecules uniformly to all 60 equivalent binding sites, canine parvovirus, which appears to have a preferred receptor-binding site, and bacteriophage T4, which gains major biological advantages on account of its unique vertex and tail organelle. [source] The absence of inorganic salt is required for the crystallization of the complete oligomerization domain of Salmonella typhimurium histone-like nucleoid-structuring proteinACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 4 2010Paul G. Leonard The histone-like nucleoid-structuring protein (H-NS) plays an important role in both DNA packaging and global gene regulation in enterobacteria. Self-association of the N-terminal domain results in polydisperse oligomers that are critical to the function of the protein. This heterogeneity in oligomer size has so far prevented structure determination of the complete oligomerization domain by NMR or X-ray crystallography. In the absence of inorganic salt, the H-NS oligomerization domain is predominantly restricted to an equilibrium between a homodimer and homotetramer, allowing a protein solution to be prepared that is sufficiently homogeneous for successful crystallization. Crystallization was achieved by tailoring the conditions screened to those identified as minimizing the potential disruption of protein-solution homogeneity. This finding provides a significant step towards resolving the structure of this important prokaryotic protein. [source] | ||||||||||