Assuntos
Archaea/genética , Bactérias/genética , Segregação de Cromossomos , Cromossomos de Archaea/metabolismo , Cromossomos Bacterianos/metabolismo , Archaea/fisiologia , Cromossomos de Archaea/ultraestrutura , Cromossomos Bacterianos/ultraestrutura , Modelos Biológicos , Células Procarióticas/fisiologiaRESUMO
Being distinct from bacteria and eukaryotes, Archaea constitute a third domain of living things. The DNA replication, transcription, and translation machineries of Archaea are more similar to those of eukaryotes, whereas the genes involved in metabolic processes show more similarity to their bacterial counterparts. We report here that TK0471/TrmB-like 2 (TrmBL2), in addition to histone, is a novel type of abundant chromosomal protein in the model euryarchaeon Thermococcus kodakarensis . The chromosome of T. kodakarensis can be separated into regions enriched either with histone, in which the genetic material takes on a "beads-on-a-string" appearance, or with TK0471/TrmBL2, in which it assumes a thick fibrous structure. TK0471/TrmBL2 binds to both coding and intergenic regions and represses transcription when bound to the promoter region. These results show that the archaeal chromosome is organized into heterogeneous structures and that TK0471/TrmBL2 acts as a general chromosomal protein as well as a global transcriptional repressor.
Assuntos
Proteínas Arqueais/metabolismo , Proteínas Cromossômicas não Histona/metabolismo , Cromossomos de Archaea/ultraestrutura , Genoma Arqueal , Histonas/metabolismo , Thermococcus/genética , Proteínas Arqueais/química , Proteínas Arqueais/genética , Proteínas Arqueais/ultraestrutura , Proteínas Cromossômicas não Histona/química , Proteínas Cromossômicas não Histona/genética , Proteínas Cromossômicas não Histona/ultraestrutura , DNA Arqueal/química , DNA Arqueal/ultraestrutura , Deleção de Genes , Regulação da Expressão Gênica em Archaea , Histonas/química , Histonas/ultraestrutura , Thermococcus/ultraestrutura , Regulação para CimaRESUMO
SMC (structural maintenance of chromosomes) proteins are highly conserved and present in eukaryotes, bacteria and archaea. They function in chromosome condensation and segregation and in DNA repair. Using an insertion vector containing the pac gene for resistance to puromycin, we have created an insertion in the smc gene of Methanococcus voltae. We used epifluorescence microscopy to examine the cell and nucleoid morphology, DNA content and metabolic activity. This insertion causes gross defects in chromosome segregation and cell morphology. Approximately 20% of mutant cells contain little or no DNA, and a subset of cells ( approximately 2%) IS abnormally large (three to four times their normal diameter) titan cells. We believe that these titan cells indicate cell division arrest at a cell cycle checkpoint. The results confirm that SMC in archaea is an important player in chromosome dynamics (as it is in bacteria and eukaryotes).
