A helicase-tethered ORC flip enables bidirectional helicase loading
<jats:p>Replication origins are licensed by loading two Mcm2-7 helicases around DNA in a head-to-head conformation poised to initiate bidirectional replication. This process requires origin–recognition complex (ORC), Cdc6, and Cdt1. Although different Cdc6 and Cdt1 molecules load each helicase...
| Main Authors: | , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | English |
| Published: |
eLife Sciences Publications, Ltd
2022
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| Online Access: | https://hdl.handle.net/1721.1/146767 |
| _version_ | 1826211000684118016 |
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| author | Gupta, Shalini Friedman, Larry J Gelles, Jeff Bell, Stephen P |
| author2 | Massachusetts Institute of Technology. Department of Biology |
| author_facet | Massachusetts Institute of Technology. Department of Biology Gupta, Shalini Friedman, Larry J Gelles, Jeff Bell, Stephen P |
| author_sort | Gupta, Shalini |
| collection | MIT |
| description | <jats:p>Replication origins are licensed by loading two Mcm2-7 helicases around DNA in a head-to-head conformation poised to initiate bidirectional replication. This process requires origin–recognition complex (ORC), Cdc6, and Cdt1. Although different Cdc6 and Cdt1 molecules load each helicase, whether two ORC proteins are required is unclear. Using colocalization single-molecule spectroscopy combined with single-molecule Förster resonance energy transfer (FRET), we investigated interactions between ORC and Mcm2-7 during helicase loading. In the large majority of events, we observed a single ORC molecule recruiting both Mcm2-7/Cdt1 complexes via similar interactions that end upon Cdt1 release. Between first- and second-helicase recruitment, a rapid change in interactions between ORC and the first Mcm2-7 occurs. Within seconds, ORC breaks the interactions mediating first Mcm2-7 recruitment, releases from its initial DNA-binding site, and forms a new interaction with the opposite face of the first Mcm2-7. This rearrangement requires release of the first Cdt1 and tethers ORC as it flips over the first Mcm2-7 to form an inverted Mcm2-7–ORC–DNA complex required for second-helicase recruitment. To ensure correct licensing, this complex is maintained until head-to-head interactions between the two helicases are formed. Our findings reconcile previous observations and reveal a highly coordinated series of events through which a single ORC molecule can load two oppositely oriented helicases.</jats:p> |
| first_indexed | 2024-09-23T14:59:10Z |
| format | Article |
| id | mit-1721.1/146767 |
| institution | Massachusetts Institute of Technology |
| language | English |
| last_indexed | 2024-09-23T14:59:10Z |
| publishDate | 2022 |
| publisher | eLife Sciences Publications, Ltd |
| record_format | dspace |
| spelling | mit-1721.1/1467672022-12-07T03:09:59Z A helicase-tethered ORC flip enables bidirectional helicase loading Gupta, Shalini Friedman, Larry J Gelles, Jeff Bell, Stephen P Massachusetts Institute of Technology. Department of Biology <jats:p>Replication origins are licensed by loading two Mcm2-7 helicases around DNA in a head-to-head conformation poised to initiate bidirectional replication. This process requires origin–recognition complex (ORC), Cdc6, and Cdt1. Although different Cdc6 and Cdt1 molecules load each helicase, whether two ORC proteins are required is unclear. Using colocalization single-molecule spectroscopy combined with single-molecule Förster resonance energy transfer (FRET), we investigated interactions between ORC and Mcm2-7 during helicase loading. In the large majority of events, we observed a single ORC molecule recruiting both Mcm2-7/Cdt1 complexes via similar interactions that end upon Cdt1 release. Between first- and second-helicase recruitment, a rapid change in interactions between ORC and the first Mcm2-7 occurs. Within seconds, ORC breaks the interactions mediating first Mcm2-7 recruitment, releases from its initial DNA-binding site, and forms a new interaction with the opposite face of the first Mcm2-7. This rearrangement requires release of the first Cdt1 and tethers ORC as it flips over the first Mcm2-7 to form an inverted Mcm2-7–ORC–DNA complex required for second-helicase recruitment. To ensure correct licensing, this complex is maintained until head-to-head interactions between the two helicases are formed. Our findings reconcile previous observations and reveal a highly coordinated series of events through which a single ORC molecule can load two oppositely oriented helicases.</jats:p> 2022-12-06T19:14:10Z 2022-12-06T19:14:10Z 2021 2022-12-06T18:34:32Z Article http://purl.org/eprint/type/JournalArticle https://hdl.handle.net/1721.1/146767 Gupta, Shalini, Friedman, Larry J, Gelles, Jeff and Bell, Stephen P. 2021. "A helicase-tethered ORC flip enables bidirectional helicase loading." eLife, 10. en 10.7554/ELIFE.74282 eLife Creative Commons Attribution 4.0 International license https://creativecommons.org/licenses/by/4.0/ application/pdf eLife Sciences Publications, Ltd eLife |
| spellingShingle | Gupta, Shalini Friedman, Larry J Gelles, Jeff Bell, Stephen P A helicase-tethered ORC flip enables bidirectional helicase loading |
| title | A helicase-tethered ORC flip enables bidirectional helicase loading |
| title_full | A helicase-tethered ORC flip enables bidirectional helicase loading |
| title_fullStr | A helicase-tethered ORC flip enables bidirectional helicase loading |
| title_full_unstemmed | A helicase-tethered ORC flip enables bidirectional helicase loading |
| title_short | A helicase-tethered ORC flip enables bidirectional helicase loading |
| title_sort | helicase tethered orc flip enables bidirectional helicase loading |
| url | https://hdl.handle.net/1721.1/146767 |
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