Identification of replication origins in the genome of the methanogenic archaeon, Methanocaldococcus jannaschii.
Methanocaldococcus jannaschii has been notorious as an archaeon in which the replication origins are difficult to identify. Although extensive efforts have been exerted on this issue, the locations of replication origins still remain elusive 7 years after the publication of its complete genome sequence in 1996. Ambiguous results were obtained in identifying the replication origins of M. jannaschii based on all theoretical and experimental approaches. In the genome of M. jannaschii, we found that an ORF (MJ0774), annotated as a hypothetical protein, is a homologue of the Cdc6 protein. The position of the gene is at a global minimum of the x component of the Z curve, i.e., RY disparity curve, which has been used to identify replication origins in other Archaea. In addition, an intergenic region (694,540-695,226 bp) that is between the cdc6 gene and an adjacent ORF shows almost all the characteristics of known replication origins, i.e., it is highly rich in AT composition (80%) and contains multiple copies of repeat elements and AT stretches. Therefore, these lines of evidence strongly suggest that the identified region is a replication origin, which is designated as oriC1. The analysis of the y component of the Z curve, i.e., MK disparity curve, suggests the presence of another replication origin corresponding to one of the peaks in the MK disparity curve at around 1,388 kb of the genome.
Zhang
Ren
R
Department of Epidemiology and Biostatistics, Tianjin Cancer Institute and Hospital, 300060 Tianjin, China.
Zhang
Chun-Ting
CT
D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics; D001482:Base Composition; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics; D019641:DNA, Archaeal / Q000737:chemistry / Q000235:genetics; D020745:Genome, Archaeal; D017015:Methanococcales / Q000235:genetics*; D008969:Molecular Sequence Data; D018741:Replication Origin; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics; D017386:Sequence Homology, Amino Acid
D019843:Archaeal Proteins; C066503:CDC6 protein, S cerevisiae; D018797:Cell Cycle Proteins; D019641:DNA, Archaeal; D029701:Saccharomyces cerevisiae Proteins