J Syst Evol ›› 2008, Vol. 46 ›› Issue (3): 405-423.DOI: 10.3724/SP.J.1002.2008.08031

• Research Articles • Previous Articles     Next Articles

Long-term maintenance of stable copy number in the eukaryotic SMC family: origin of a vertebrate meiotic SMC1 and fate of recent segmental duplicates

1 4Alexandra SURCEL, 1 2Xiaofan ZHOU*, 2 3Li QUAN, 1 2Hong MA*   

  1. 1(The Intercollege Graduate Program in Cell and Developmental Biology, The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA)

    2(Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA)

    3(The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA)

    4(Present address: Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA)
    hxm16@psu.edu
  • Received:2008-03-05 Published:2008-05-18

Abstract: Members of the Structural Maintenance of Chromosome (SMC) family have long been of interest to molecular and evolutionary biologists for their role in chromosome structural dynamics, particularly sister chromatid cohesion, condensation, and DNA repair. SMC and related proteins are found in all major groups of living organisms and share a common structure of conserved N and C globular domains separated from the conserved hinge domain by long coiled-coil regions. In eukaryotes there are six paralogous proteins that form three het-erodimeric pairs, whereas in prokaryotes there is only one SMC protein that homodimerizes. From recently com-pleted genome sequences, we have identified SMC genes from 34 eukaryotes that have not been described in previous reports. Our phylogenetic analysis of these and previously identified SMC genes supports an origin for the vertebrate meiotic SMC1 in the most recent common ancestor since the divergence from invertebrate animals. Additionally, we have identified duplicate copies due to segmental duplications for some of the SMC paralogs in plants and yeast, mainly SMC2 and SMC6, and detected evidence that duplicates of other paralogs were lost, suggesting differential evolution for these genes. Our analysis indicates that the SMC paralogs have been stably maintained at very low copy numbers, even after segmental (genome-wide) duplications. It is possible that such low copy numbers might be selected during eukaryotic evolution, although other possibilities are not ruled out.

Key words: cohesin, condensin, meiosis, segmental duplication, SMC