We analyzed the chromosome region of Streptococcus pneumoniae located downstream of the division and cell wall (dcw) cluster that contains the homolog of the Bacillus subtilis cell division gene divIVA and some genes of unknown function. Inactivation of divIVA in S. pneumoniae resulted in severe growth inhibition and defects in cell shape, nucleoid segregation, and cell division. Inactivation of the ylm genes resulted in some morphological and/or division abnormalities, depending on the inactivated gene. Transcriptional analysis revealed a relationship between these genes and the ftsA and ftsZ cell division genes, also indicating that the connection between the dcw cluster and the divIVA region is more extensive than just chromosomal position and gene organization.Historically, most of the available information about bacterial cell division comes from the intensively studied gramnegative rod Escherichia coli and the gram-positive rod Bacillus subtilis (reviewed in references 1, 9, 10, 15, 17, and 24). This situation is changing, due to both the increasing interest in the field of cell division and the availability of genomic data. Most of the cell division genes have now been identified in a wide range of bacteria, and despite the differences observed among species, many of these genes are found organized in a chromosomal region corresponding to the 2-min region of the E. coli chromosome known as the dcw (for "division and cell wall") cluster.Notwithstanding the large amount of sequence information, very little is known about the molecular mechanism that regulates cell division in bacteria other than the model organisms and cell division in gram-positive cocci remains poorly understood. However, some extrapolations from the analysis of the Fts proteins that are essential for cell division, in particular the FtsZ protein, the major component of the septal ring structure (15), suggest that the basic mechanism involved in septum formation should not differ from cocci to rods.A more intriguing problem and one that shows significantly less conservation is how different bacteria operate the division site selection mechanism that ensures correct FtsZ positioning at midcell. In E. coli, the correct division site at the center is distinguished from the other potential division sites at the poles through the combined action of three proteins, MinC, MinD, and MinE, encoded by the minCDE genes (5, 6, 21).In B. subtilis, divIVB encodes the MinC and MinD homologs but not the MinE homolog (13, 26). The DivIVA protein has been proposed to play a role in the control of division site selection as the functional counterpart of the missing MinE in B. subtilis (3,7,18,19). Recently, we identified a Streptococcus pneumoniae gene encoding the B. subtilis DivIVA homolog (20). We noted that divIVA is the last gene of a region located downstream of the cell division genes ftsA to ftsZ and is conserved in the same position in a number of gram-positive cocci. In addition to divIVA, the region contains some open reading frames of unknown fu...
The public availability of numerous microbial genomes is enabling the analysis of bacterial biology in great detail and with an unprecedented, organism-wide and taxon-wide, broad scope. Streptococcus pneumoniae is one of the most important bacterial pathogens throughout the world. We present here sequences and functional annotations for 2.1-Mbp of pneumococcal DNA, covering more than 90% of the total estimated size of the genome. The sequenced strain is a clinical isolate resistant to macrolides and tetracycline. It carries a type 19F capsular locus, but multilocus sequence typing for several conserved genetic loci suggests that the strain sequenced belongs to a pneumococcal lineage that most often expresses a serotype 15 capsular polysaccharide. A total of 2,046 putative open reading frames (ORFs) longer than 100 amino acids were identified (average of 1,009 bp per ORF), including all described two-component systems and aminoacyl tRNA synthetases. Comparisons to other complete, or nearly complete, bacterial genomes were made and are presented in a graphical form for all the predicted proteins.
Diacylglycerol kinases are key modulators of levels of diacylglycerol, a second messenger involved in a variety of cellular responses to extracellular stimuli. A number of diacylglycerol kinases encoded by separate genes are present in mammalian genomes. We have cloned cDNAs encoding several isoforms of the human homologue of the rat diacylglycerol kinase  gene and characterized two such isoforms that differ at their carboxyl terminus through alternative splicing and the usage of different polyadenylation signals. Quantitative analysis of gene expression in a panel of human tissue cDNAs revealed that transcripts corresponding to both isoforms are coexpressed in central nervous system tissues and in the uterus, with one variant being expressed at relatively higher levels. As green fluorescent protein fusions, the two isoforms displayed localization to different subcellular compartments, with one variant being associated with the plasma membrane, while the other isoform was predominantly localized within the cytoplasm. Differences were also observed in their subcellular localization in response to phorbol ester stimulation. Enzymatic assays demonstrated that the two isoforms display comparable diacylglycerol kinase activities. Therefore, the human diacylglycerol kinase  gene can generate several enzyme isoforms, which can display different expression levels and subcellular localization but similar enzymatic activities in vitro.Diacylglycerol (DG) 1 represents a key signaling intermediate downstream of Gq/phospholipase C- coupled receptors. It is synthesized by phospholipase C- from phosphoinositides as a response to a variety of molecules involved in intercellular communication, including hormones, neurotransmitters, and growth factors. The best known target of DG action is protein kinase C (PKC), whose activity plays a central role in the control of proliferation and differentiation of many different cell types (1). In addition, DG can also modulate the activity of intracellular proteins such as members of the Rho and Ras families, thus potentially affecting other cellular functions such as cytoskeletal organization (2). The control of steady-state cellular levels of DG is therefore crucial to normal cellular physiology. The signaling properties of DG are terminated by its conversion to phosphatidic acid (itself a second messenger, reviewed in Ref. 3, through the action of diacylglycerol kinases (DGKs), a class of evolutionary conserved enzymes presently counting nine mammalian subtypes encoded by separate genes (␣, , ␥, ␦, ⑀, , , , ; reviewed in Ref. 4). The cloning of DGK genes from several mammalian species (5-19) has allowed an analysis of the domain architecture of these proteins. Structurally, mammalian DGK subtypes are characterized by the presence of conserved domains, common to all subtypes and of additional subtype-specific functional domains, which allow their grouping into five separate classes (3, 4). The functional domains shared by all DGK subtypes comprise the catalytic (kinase) domain and a ...
A systematic study on the mRNA species expressed in the human skeletal muscle is presented in this paper. To carry on this study, a new method has been developed for the construction of unbiased cDNA libraries specially designed for the production of ESTs corresponding to the 3'-end portion of the mRNAs. The method has been applied to human skeletal muscle, where the analysis of the transcription profile is particularly difficult for the presence of several very abundant transcripts. To detect and quantify high-level mRNAs, the first 1054 ESTs were obtained from randomly selected clones. The 10 most abundant transcripts accounted for >45% of the clones. Subsequently, these transcripts were identified by filter hybridization, thus making DNA sequencing more productive. Overall, 4370 clones were identified: 3372 by DNA sequencing and 998 by filter hybridization. The number of groups of sequences identifying individual transcripts was relatively low compared with other tissues, resulting in a total of 934 groups out of 4370 ESTs. Of these, 719 groups were represented by only one sequence.
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