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Gordon SG, Rog O. Building the synaptonemal complex: Molecular interactions between the axis and the central region. PLoS Genet 2023; 19:e1010822. [PMID: 37471284 PMCID: PMC10359014 DOI: 10.1371/journal.pgen.1010822] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/22/2023] Open
Abstract
The successful delivery of genetic material to gametes requires tightly regulated interactions between the parental chromosomes. Central to this regulation is a conserved chromosomal interface called the synaptonemal complex (SC), which brings the parental chromosomes in close proximity along their length. While many of its components are known, the interfaces that mediate the assembly of the SC remain a mystery. Here, we survey findings from different model systems while focusing on insight gained in the nematode C. elegans. We synthesize our current understanding of the structure, dynamics, and biophysical properties of the SC and propose mechanisms for SC assembly.
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Affiliation(s)
- Spencer G. Gordon
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, Utah, United States of America
| | - Ofer Rog
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, Utah, United States of America
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Billmyre KK. Chromosome-specific behaviors during early meiosis. Curr Top Dev Biol 2022; 151:127-154. [PMID: 36681468 DOI: 10.1016/bs.ctdb.2022.05.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Inheriting the wrong number of chromosomes is one of the leading causes of infertility and birth defects in humans. However, in many organisms, individual chromosomes vary dramatically in both organization, sequence, and size. Chromosome segregation systems must be capable of accounting for these differences to reliably segregate chromosomes. During gametogenesis, meiosis ensures that all chromosomes segregate properly into gametes (i.e., egg or sperm). Interestingly, not all chromosomes exhibit the same dynamics during meiosis, which can lead to chromosome-specific behaviors and defects. This review will summarize some of the chromosome-specific meiotic events that are currently known and discuss their impact on meiotic outcomes.
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Chen J, Huang Y, Zhang K. The DEAD-Box Protein Rok1 Coordinates Ribosomal RNA Processing in Association with Rrp5 in Drosophila. Int J Mol Sci 2022; 23:ijms23105685. [PMID: 35628496 PMCID: PMC9146779 DOI: 10.3390/ijms23105685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 05/09/2022] [Accepted: 05/17/2022] [Indexed: 02/04/2023] Open
Abstract
Ribosome biogenesis and processing involve the coordinated action of many components. The DEAD-box RNA helicase (Rok1) is essential for cell viability, and the depletion of Rok1 inhibits pre-rRNA processing. Previous research on Rok1 and its cofactor Rrp5 has been performed primarily in yeast. Few functional studies have been performed in complex multicellular eukaryotes. Here, we used a combination of genetics and developmental experiments to show that Rok1 and Rrp5, which localize to the nucleolus, play key roles in the pre-rRNA processing and ribosome assembly in D. melanogaster. The accumulation of pre-rRNAs caused by Rok1 depletion can result in developmental defects. The loss of Rok1 enlarged the nucleolus and led to stalled ribosome assembly and pre-rRNA processing in the nucleolus, thereby blocking rRNA maturation and exacerbating the inhibition of mitosis in the brain. We also discovered that rrp54-2/4-2 displayed significantly increased ITS1 signaling by fluorescence in situ hybridization, and a reduction in ITS2. Rrp5 signal was highly enriched in the core of the nucleolus in the rok1167/167 mutant, suggesting that Rok1 is required for the accurate cellular localization of Rrp5 in the nucleolus. We have thus uncovered functions of Rok1 that reveal important implications for ribosome processing in eukaryotes.
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Affiliation(s)
- Jie Chen
- Guangdong Provincial Key Laboratory of High Technology for Plant Protection, Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China;
- Correspondence: (J.C.); (Y.H.); Tel.: +86-20-87597440 (J.C.)
| | - Yuantai Huang
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China;
- Correspondence: (J.C.); (Y.H.); Tel.: +86-20-87597440 (J.C.)
| | - Kang Zhang
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China;
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Kursel LE, Cope HD, Rog O. Unconventional conservation reveals structure-function relationships in the synaptonemal complex. eLife 2021; 10:72061. [PMID: 34787570 PMCID: PMC8598163 DOI: 10.7554/elife.72061] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 10/21/2021] [Indexed: 12/29/2022] Open
Abstract
Functional requirements constrain protein evolution, commonly manifesting in a conserved amino acid sequence. Here, we extend this idea to secondary structural features by tracking their conservation in essential meiotic proteins with highly diverged sequences. The synaptonemal complex (SC) is a ~100-nm-wide ladder-like meiotic structure present in all eukaryotic clades, where it aligns parental chromosomes and regulates exchanges between them. Despite the conserved ultrastructure and functions of the SC, SC proteins are highly divergent within Caenorhabditis. However, SC proteins have highly conserved length and coiled-coil domain structure. We found the same unconventional conservation signature in Drosophila and mammals, and used it to identify a novel SC protein in Pristionchus pacificus, Ppa-SYP-1. Our work suggests that coiled-coils play wide-ranging roles in the structure and function of the SC, and more broadly, that expanding sequence analysis beyond measures of per-site similarity can enhance our understanding of protein evolution and function.
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Affiliation(s)
- Lisa E Kursel
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, United States
| | - Henry D Cope
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, United States
| | - Ofer Rog
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, United States
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Huang W, Liu Z, Rong YS. Dynamic localization of DNA topoisomerase I and its functional relevance during Drosophila development. G3-GENES GENOMES GENETICS 2021; 11:6298592. [PMID: 34544118 PMCID: PMC8661406 DOI: 10.1093/g3journal/jkab202] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Accepted: 06/09/2021] [Indexed: 11/23/2022]
Abstract
DNA topoisomerase I (Top1) maintains chromatin conformation during transcription. While Top1 is not essential in simple eukaryotic organisms such as yeast, it is required for the development of multicellular organisms. In fact, tissue and cell-type-specific functions of Top1 have been suggested in the fruit fly Drosophila. A better understanding of Top1’s function in the context of development is important as Top1 inhibitors are among the most widely used anticancer drugs. As a step toward such a better understanding, we studied its localization in live cells of Drosophila. Consistent with prior results, Top1 is highly enriched at the nucleolus in transcriptionally active polyploid cells, and this enrichment responds to perturbation of transcription. In diploid cells, we uncovered evidence for Top1 foci formation at genomic regions not limited to the active rDNA locus, suggestive of novel regulation of Top1 recruitment. In the male germline, Top1 is highly enriched at the paired rDNA loci on sex chromosomes suggesting that it might participate in regulating their segregation during meiosis. Results from RNAi-mediated Top1 knockdown lend support to this hypothesis. Our study has provided one of the most comprehensive descriptions of Top1 localization during animal development.
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Affiliation(s)
- Wuqiang Huang
- School of Life Sciences, Sun Yat-sen University, Guangzhou, Guangdong Province, 510275, China.,Hengyang College of Medicine, University of South China, Hengyang 421001, China
| | - Zhiping Liu
- School of Life Sciences, Sun Yat-sen University, Guangzhou, Guangdong Province, 510275, China
| | - Yikang S Rong
- Hengyang College of Medicine, University of South China, Hengyang 421001, China
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Gordon SG, Kursel LE, Xu K, Rog O. Synaptonemal Complex dimerization regulates chromosome alignment and crossover patterning in meiosis. PLoS Genet 2021; 17:e1009205. [PMID: 33730019 PMCID: PMC7968687 DOI: 10.1371/journal.pgen.1009205] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Accepted: 02/15/2021] [Indexed: 12/30/2022] Open
Abstract
During sexual reproduction the parental homologous chromosomes find each other (pair) and align along their lengths by integrating local sequence homology with large-scale contiguity, thereby allowing for precise exchange of genetic information. The Synaptonemal Complex (SC) is a conserved zipper-like structure that assembles between the homologous chromosomes, bringing them together and regulating exchanges between them. However, the molecular mechanisms by which the SC carries out these functions remain poorly understood. Here we isolated and characterized two mutations in the dimerization interface in the middle of the SC zipper in C. elegans. The mutations perturb both chromosome alignment and the regulation of genetic exchanges. Underlying the chromosome-scale phenotypes are distinct alterations to the way SC subunits interact with one another. We propose a model whereby the SC brings homologous chromosomes together through two activities: obligate zipping that prevents assembly on unpaired chromosomes; and a tendency to extend pairing interactions along the entire length of the chromosomes.
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Affiliation(s)
- Spencer G. Gordon
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, United States of America
| | - Lisa E. Kursel
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, United States of America
| | - Kewei Xu
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, United States of America
| | - Ofer Rog
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, United States of America
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Wesley ER, Hawley RS, Billmyre KK. Genetic background impacts the timing of synaptonemal complex breakdown in Drosophila melanogaster. Chromosoma 2020; 129:243-254. [PMID: 33068154 PMCID: PMC7666587 DOI: 10.1007/s00412-020-00742-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 10/05/2020] [Accepted: 10/06/2020] [Indexed: 11/16/2022]
Abstract
Experiments performed in different genetic backgrounds occasionally exhibit failure in experimental reproducibility. This is a serious issue in Drosophila where there are no standard control stocks. Here, we illustrate the importance of controlling genetic background by showing that the timing of a major meiotic event, the breakdown of the synaptonemal complex (SC), varies in different genetic backgrounds. We assessed SC breakdown in three different control stocks and found that in one control stock, y w; svspa-pol, the SC broke down earlier than in Oregon-R and w1118 stocks. We further examined SC breakdown in these three control backgrounds with flies heterozygous for a null mutation in c(3)G, which encodes a key structural component of the SC. Flies heterozygous for c(3)G displayed differences in the timing of SC breakdown in different control backgrounds, providing evidence of a sensitizing effect of this mutation. These observations suggest that SC maintenance is associated with the dosage of c(3)G in some backgrounds. Lastly, chromosome segregation was not affected by premature SC breakdown in mid-prophase, consistent with previous findings that chromosome segregation is not dependent on full-length SC in mid-prophase. Thus, genetic background is an important variable to consider with respect to SC behavior during Drosophila meiosis.
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Affiliation(s)
- Emily R Wesley
- Stowers Institute for Medical Research, Kansas City, MO, 64110, USA.,University of Missouri-Kansas City, Kansas City, MO, 64110, USA
| | - R Scott Hawley
- Stowers Institute for Medical Research, Kansas City, MO, 64110, USA. .,Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS, 66160, USA.
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