Identification of replication origins in the genom

Authors: Ren Zhang ChunTing Zhang

Publish Date: 2004/04/09

Volume: 8, Issue: 3, Pages: 253-258

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Abstract

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 ie RY disparity curve which has been used to identify replication origins in other Archaea In addition an intergenic region 694540–695226 bp that is between the cdc6 gene and an adjacent ORF shows almost all the characteristics of known replication origins ie 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 ie MK disparity curve suggests the presence of another replication origin corresponding to one of the peaks in the MK disparity curve at around 1388 kb of the genome

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