Dinoflagellates have unique chromosomes that are in a permanently condensed liquid crystalline state and are devoid of core histones. In order to determine the protein factors contributing to these remarkable features, I tried to characterize the property of Condensin in dinoflagellate chromosomes. Condensin is a protein complex required for normal chromosome condensation and segregation in all domains of life. Mutations in Condensin subunits in prokaryotes and eukaryotes cause chromosome condensation defects and segregation failure....[ Read more ]

Dinoflagellates have unique chromosomes that are in a permanently condensed liquid crystalline state and are devoid of core histones. In order to determine the protein factors contributing to these remarkable features, I tried to characterize the property of Condensin in dinoflagellate chromosomes. Condensin is a protein complex required for normal chromosome condensation and segregation in all domains of life. Mutations in Condensin subunits in prokaryotes and eukaryotes cause chromosome condensation defects and segregation failure.

Full-length cDNAs of Condensin subunit SMC2 and SMC4 (SMC-Structural Maintenance of Chromosome) were cloned from cDNAs of dinoflagellate Crypthecodinium cohnii by taking advantage of the conserved SMC protein sequence and Conserved Splicing Leader of dinoflagellate mRNA. In silico analysis showed that the two genes contain all the basic features of SMC proteins. Surprisingly, the dinoflagellate SMC2 and SMC4 are more affiliated with plant orthologues, rather than other known Aveolate orthologues in terms of phylogenetic analysis.

The active recombinant proteins of SMC2 and SMC4 were produced by Baculovirus-insect cell system. They are biochemically similar to their orthologues in terms of DNA binding activities. By monitoring the expression level of its subunit SMC2, I found that the amount of Condensin peak at G2/M phase of the cell cycle which is different from other eukaryotes. Furthermore, the extraction of C. cohnii Condensin by NaCl correlates with the disruption of chromosome structures. Our evidences suggest that C. cohnii Condensin may involve in mitosis as well as play important roles in maintaining the structure of permanently condensed chromosomes at interphase. Possible roles and functional mechanism of Condensin in dinoflagellate chromosomes were discussed.