Diverse Mitotic and Interphase Functions of Condensins in Drosophila

Abstract

The condensin complex has been implicated in the higher-order organization of mitotic chromosomes in a host of model eukaryotes from yeasts to flies and vertebrates. Although chromosomes paradoxically appear to condense in condensin mutants, chromatids are not properly resolved, resulting in chromosome segregation defects during anaphase. We have examined the role of different condensin complex components in interphase chromatin function by examining the effects of various condensin mutations on position-effect variegation in Drosophila melanogaster. Surprisingly, most mutations affecting condensin proteins were often found to result in strong enhancement of variegation in contrast to what might be expected for proteins believed to compact the genome. This suggests either that the role of condensin proteins in interphase differs from their expected role in mitosis or that the way we envision condensin's activity needs to be modified to accommodate alternative possibilities.

Transcriptional homogenization of rDNA repeats in the episome-based nucleolus induces genome-wide changes in the chromosomal distribution of condensin

“…Similar complexes exist in higher eukaryotes (Hirano et al, 1997;Schmiesing et al, 1998;Sutani et al, 1999;Freeman et al, 2000;Kimura et al, 2001). Dysfunction of any condensin subunit results in impaired mitotic and meiotic chromosome segregation (Strunnikov et al, 1995;Bhat et al, 1996;Freeman et al, 2000;Ouspenski et al, 2000;Hagstrom et al, 2002;Hudson et al, 2003;Ono et al, 2003;Cobbe et al, 2006).…”

Impact of a selfish B chromosome on chromatin dynamics and nuclear organization in Nasonia

“…At least two forms of the Condensin complex, each defined by different subsets of associating proteins, appear to play distinct but interrelated roles in the conversion of chromatin into distinct chromosomes (Hirota et al, 2004;Cobbe et al, 2006). At the core of these complexes are two proteins, SMC2 and SMC4 (Hirano, 2005;Cobbe et al, 2006). We reasoned that PSR-induced hypercondensation of the paternal chromatin may involve abnormal Condensin localization as a result of inappropriate PH3S10 persistence.…”

“…Specifically, this mark is though to be necessary for the loading of Condensins to chromatin (Ono et al, 2003;Hirano, 2005;Cobbe et al, 2006). At least two forms of the Condensin complex, each defined by different subsets of associating proteins, appear to play distinct but interrelated roles in the conversion of chromatin into distinct chromosomes (Hirota et al, 2004;Cobbe et al, 2006).…”

“…We reasoned that PSR-induced hypercondensation of the paternal chromatin may involve abnormal Condensin localization as a result of inappropriate PH3S10 persistence. To test this idea, we stained wild-type and PSRpositive embryos with an antibody raised against Drosophila melanogaster SMC2 ( Cobbe et al, 2006). This antibody strongly labeled metaphase chromosomes but not interphase chromatin in older wild-type embryos (Fig.…”

Facing the Correct Pole: The Challenge of Orienting Chromosomes for Meiotic Divisions

“…The single yeast condensin is most similar to the condensin I complex of higher eukaryotes. Although their exact molecular contribution to chromosome packaging remains a mystery, condensin complexes are essential for the precise organization and structural integrity of chromosomes (Bhat et al, 1996;Chan et al, 2004;Cobbe et al, 2006;Coelho et al, 2003;Dej et al, 2004;Gerlich et al, 2006;Hagstrom et al, 2002;Hartl et al, 2008;Hirota et al, 2004;Hudson et al, 2003;Lieb et al, 1998;Oliveira et al, 2003Oliveira et al, , 2005Ono et al, 2003Ono et al, , 2004Ribeiro et al, 2009;Samoshkin et al, 2009;Savvidou et al, 2005;Siddiqui et al, 2003;Stear and Roth, 2002;Steffensen et al, 2001;Vagnarelli et al, 2006;Watrin and Legagneux, 2005;Wignall et al, 2003;Koshland, 2003, 2005). SMC2 and 4 were originally identified as structural components of mitotic chromosomes in Xenopus and chicken cells (Hirano and Mitchison, 1994;Saitoh et al, 1994) and as important regulators of chromosome condensation and segregation in budding and fission yeast (Saka et al, 1994;Strunnikov et al, 1995).…”