Limits...
Condensin restructures chromosomes in preparation for meiotic divisions.

Chan RC, Severson AF, Meyer BJ - J. Cell Biol. (2004)

Bottom Line: We showed that condensin, the protein complex needed for mitotic chromosome compaction, restructures chromosomes during meiosis in Caenorhabditis elegans.Condensin helps resolve cohesin-independent linkages between sister chromatids and alleviates recombination-independent linkages between homologues.The safeguarding of chromosome resolution by condensin permits chromosome segregation and is crucial for the formation of discrete, individualized bivalent chromosomes.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.

ABSTRACT
The production of haploid gametes from diploid germ cells requires two rounds of meiotic chromosome segregation after one round of replication. Accurate meiotic chromosome segregation involves the remodeling of each pair of homologous chromosomes around the site of crossover into a highly condensed and ordered structure. We showed that condensin, the protein complex needed for mitotic chromosome compaction, restructures chromosomes during meiosis in Caenorhabditis elegans. In particular, condensin promotes both meiotic chromosome condensation after crossover recombination and the remodeling of sister chromatids. Condensin helps resolve cohesin-independent linkages between sister chromatids and alleviates recombination-independent linkages between homologues. The safeguarding of chromosome resolution by condensin permits chromosome segregation and is crucial for the formation of discrete, individualized bivalent chromosomes.

Show MeSH

Related in: MedlinePlus

HCP-6 associates exclusively with the mitotic condensin II complex and colocalizes with MIX-1 on mitotic chromosomes. (A) Coomassie staining and microsequencing identified proteins in MIX-1 IPs. (B) Western blot analysis of MIX-1, DPY-28, and HCP-6 IPs confirmed association of DPY-28 and HCP-6 with MIX-1. Dosage compensation proteins DPY-26 and DPY-27 were found only in DPY-28 and MIX-1 IPs (lane 2), and mitotic condensin subunit SMC-4 only in HCP-6 and MIX-1 IPs (lane 3). Blots were probed with mixtures of antibodies. (C) HCP-6 protein levels were not reduced in hcp-6(mr17) mutants relative to the MIX-1 and SMC-1 loading controls, but HCP-6 was undetectable in hcp-6(mr17, RNAi) mutants. (D) Phylogenetic tree comparing DPY-28, HCP-6, and CAP-D2, CAP-D3, and CAP-G homologues. HCP-6 is closest to CAP-D3 of condensin II. (E) HCP-6 and MIX-1 colocalized on metaphase chromosomes in embryos and the premeiotic germline. (F) 5S rDNA FISH revealed aneuploid nuclei in the premeiotic germline of hcp-6 mutant hermaphrodites. Bars, 5 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2172564&req=5

fig1: HCP-6 associates exclusively with the mitotic condensin II complex and colocalizes with MIX-1 on mitotic chromosomes. (A) Coomassie staining and microsequencing identified proteins in MIX-1 IPs. (B) Western blot analysis of MIX-1, DPY-28, and HCP-6 IPs confirmed association of DPY-28 and HCP-6 with MIX-1. Dosage compensation proteins DPY-26 and DPY-27 were found only in DPY-28 and MIX-1 IPs (lane 2), and mitotic condensin subunit SMC-4 only in HCP-6 and MIX-1 IPs (lane 3). Blots were probed with mixtures of antibodies. (C) HCP-6 protein levels were not reduced in hcp-6(mr17) mutants relative to the MIX-1 and SMC-1 loading controls, but HCP-6 was undetectable in hcp-6(mr17, RNAi) mutants. (D) Phylogenetic tree comparing DPY-28, HCP-6, and CAP-D2, CAP-D3, and CAP-G homologues. HCP-6 is closest to CAP-D3 of condensin II. (E) HCP-6 and MIX-1 colocalized on metaphase chromosomes in embryos and the premeiotic germline. (F) 5S rDNA FISH revealed aneuploid nuclei in the premeiotic germline of hcp-6 mutant hermaphrodites. Bars, 5 μm.

Mentions: MIX-1, the C. elegans SMC2 homologue, mediates both dosage compensation and mitotic chromosome condensation through its participation in two different condensin-like complexes (Lieb et al., 1998; Hagstrom et al., 2002). To identify non-SMC partners for MIX-1 in either complex, we immunoprecipitated both complexes from embryonic extracts using MIX-1 antibodies (Fig. 1 A). Microsequencing of proteolytic peptides from individual protein bands in the MIX-1 immunoprecipitation (IP) identified the expected dosage compensation protein DPY-27, the expected mitotic condensin subunit SMC-4, and two additional proteins (predicted products from ORFs Y39A1B.3 and Y110A7A.1). Y39A1B.3 (Mr of 160 kD) encodes the dosage compensation protein DPY-28, a homologue of the condensin I non-SMC subunit CAP-D2 (Fig. 1 D; Plenefisch et al., 1989; Tsai, C., M. Albrecht, and B. Meyer, personal communication). Y110A7A.1 (Mr of 200 kD) encodes HCP-6, a homologue of the condensin II non-SMC subunit CAP-D3 (Fig. 1 D; Ono et al., 2003; Yeong et al., 2003). HCP-6 is required for mitotic chromosome segregation (Stear and Roth, 2002). Western blot analysis confirmed the presence of all four microsequenced proteins in MIX-1 IPs and also identified the expected dosage compensation protein DPY-26 (Fig. 1 B, lane 1). The interaction of MIX-1 with HCP-6 and DPY-28 was confirmed by reciprocal IP reactions in which DPY-28 and HCP-6 antibodies precipitated MIX-1 (Fig. 1 B, lanes 2 and 3).


Condensin restructures chromosomes in preparation for meiotic divisions.

Chan RC, Severson AF, Meyer BJ - J. Cell Biol. (2004)

HCP-6 associates exclusively with the mitotic condensin II complex and colocalizes with MIX-1 on mitotic chromosomes. (A) Coomassie staining and microsequencing identified proteins in MIX-1 IPs. (B) Western blot analysis of MIX-1, DPY-28, and HCP-6 IPs confirmed association of DPY-28 and HCP-6 with MIX-1. Dosage compensation proteins DPY-26 and DPY-27 were found only in DPY-28 and MIX-1 IPs (lane 2), and mitotic condensin subunit SMC-4 only in HCP-6 and MIX-1 IPs (lane 3). Blots were probed with mixtures of antibodies. (C) HCP-6 protein levels were not reduced in hcp-6(mr17) mutants relative to the MIX-1 and SMC-1 loading controls, but HCP-6 was undetectable in hcp-6(mr17, RNAi) mutants. (D) Phylogenetic tree comparing DPY-28, HCP-6, and CAP-D2, CAP-D3, and CAP-G homologues. HCP-6 is closest to CAP-D3 of condensin II. (E) HCP-6 and MIX-1 colocalized on metaphase chromosomes in embryos and the premeiotic germline. (F) 5S rDNA FISH revealed aneuploid nuclei in the premeiotic germline of hcp-6 mutant hermaphrodites. Bars, 5 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172564&req=5

fig1: HCP-6 associates exclusively with the mitotic condensin II complex and colocalizes with MIX-1 on mitotic chromosomes. (A) Coomassie staining and microsequencing identified proteins in MIX-1 IPs. (B) Western blot analysis of MIX-1, DPY-28, and HCP-6 IPs confirmed association of DPY-28 and HCP-6 with MIX-1. Dosage compensation proteins DPY-26 and DPY-27 were found only in DPY-28 and MIX-1 IPs (lane 2), and mitotic condensin subunit SMC-4 only in HCP-6 and MIX-1 IPs (lane 3). Blots were probed with mixtures of antibodies. (C) HCP-6 protein levels were not reduced in hcp-6(mr17) mutants relative to the MIX-1 and SMC-1 loading controls, but HCP-6 was undetectable in hcp-6(mr17, RNAi) mutants. (D) Phylogenetic tree comparing DPY-28, HCP-6, and CAP-D2, CAP-D3, and CAP-G homologues. HCP-6 is closest to CAP-D3 of condensin II. (E) HCP-6 and MIX-1 colocalized on metaphase chromosomes in embryos and the premeiotic germline. (F) 5S rDNA FISH revealed aneuploid nuclei in the premeiotic germline of hcp-6 mutant hermaphrodites. Bars, 5 μm.
Mentions: MIX-1, the C. elegans SMC2 homologue, mediates both dosage compensation and mitotic chromosome condensation through its participation in two different condensin-like complexes (Lieb et al., 1998; Hagstrom et al., 2002). To identify non-SMC partners for MIX-1 in either complex, we immunoprecipitated both complexes from embryonic extracts using MIX-1 antibodies (Fig. 1 A). Microsequencing of proteolytic peptides from individual protein bands in the MIX-1 immunoprecipitation (IP) identified the expected dosage compensation protein DPY-27, the expected mitotic condensin subunit SMC-4, and two additional proteins (predicted products from ORFs Y39A1B.3 and Y110A7A.1). Y39A1B.3 (Mr of 160 kD) encodes the dosage compensation protein DPY-28, a homologue of the condensin I non-SMC subunit CAP-D2 (Fig. 1 D; Plenefisch et al., 1989; Tsai, C., M. Albrecht, and B. Meyer, personal communication). Y110A7A.1 (Mr of 200 kD) encodes HCP-6, a homologue of the condensin II non-SMC subunit CAP-D3 (Fig. 1 D; Ono et al., 2003; Yeong et al., 2003). HCP-6 is required for mitotic chromosome segregation (Stear and Roth, 2002). Western blot analysis confirmed the presence of all four microsequenced proteins in MIX-1 IPs and also identified the expected dosage compensation protein DPY-26 (Fig. 1 B, lane 1). The interaction of MIX-1 with HCP-6 and DPY-28 was confirmed by reciprocal IP reactions in which DPY-28 and HCP-6 antibodies precipitated MIX-1 (Fig. 1 B, lanes 2 and 3).

Bottom Line: We showed that condensin, the protein complex needed for mitotic chromosome compaction, restructures chromosomes during meiosis in Caenorhabditis elegans.Condensin helps resolve cohesin-independent linkages between sister chromatids and alleviates recombination-independent linkages between homologues.The safeguarding of chromosome resolution by condensin permits chromosome segregation and is crucial for the formation of discrete, individualized bivalent chromosomes.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.

ABSTRACT
The production of haploid gametes from diploid germ cells requires two rounds of meiotic chromosome segregation after one round of replication. Accurate meiotic chromosome segregation involves the remodeling of each pair of homologous chromosomes around the site of crossover into a highly condensed and ordered structure. We showed that condensin, the protein complex needed for mitotic chromosome compaction, restructures chromosomes during meiosis in Caenorhabditis elegans. In particular, condensin promotes both meiotic chromosome condensation after crossover recombination and the remodeling of sister chromatids. Condensin helps resolve cohesin-independent linkages between sister chromatids and alleviates recombination-independent linkages between homologues. The safeguarding of chromosome resolution by condensin permits chromosome segregation and is crucial for the formation of discrete, individualized bivalent chromosomes.

Show MeSH
Related in: MedlinePlus