{ "145240-21896916": { "datetime_modified":"20260218T093228", "datetime_start":"20260225T120000", "datetime_end":"20260225T130000", "has_end_time":1, "date_start":"2026-02-25", "date_end":"2026-02-25", "time_start":"12:00:00", "time_end":"13:00:00", "time_zone":"America\/Detroit", "event_title":"MCDB Dissertation Defense Seminar> Revisiting the role of DNA polymerase I in maintaining the genome integrity of Bacillus subtilis", "occurrence_title":"", "combined_title":"MCDB Dissertation Defense Seminar> Revisiting the role of DNA polymerase I in maintaining the genome integrity of Bacillus subtilis: Caroline Lowder", "event_subtitle":"Caroline Lowder", "event_type":"Workshop \/ Seminar", "event_type_id":"21", "description":"One of the essential biological findings of the past century was the discovery of DNA polymerase, which revealed the core mechanism by which DNA is faithfully replicated and repaired in cells. While polymerases were first described in bacteria, homologous proteins are present in all domains and contribute to multi-faceted systems that employ multiple DNA polymerases to optimize both fidelity and processivity. Of these, one of the most adaptable enzymes is the originally discovered bacterial polymerase, DNA polymerase I (Pol I). This protein has three distinct domains that confer different functions: a 5\u2032-3\u2032 flap endonuclease (FEN) for removing downstream nucleic acids, a 3\u2032-5\u2032 exonuclease for proofreading the nascent strand, and a 5\u2032-3\u2032 polymerase for synthesizing DNA. These three activities allow Pol I to contribute broadly to DNA repair and replication, though its canonical roles are primer removal and Okazaki fragment maturation. \n\nThe role of Pol I in primer removal, however, was established using Pol I from the gram-negative bacterium Escherichia coli and does not consider diverging functions that may have developed as bacterial lineages evolved separately. Using genetic screens and biochemical assays, we characterized Pol I and a Pol I-independent FEN from Bacillus subtilis (FEN, formerly YpcP). We demonstrate that FEN is actively involved in Okazaki fragment maturation in vivo, as cells lacking fenA are sensitive to the accumulation of RNA-DNA hybrids and this phenotype is not rescued by over-expression of polA. Using a variety of substrates, we show that FEN is a more active nuclease than Pol I. FEN showed significant activity on substrates mimicking intermediates formed during Okazaki fragment maturation (5\u2032, 3\u2032 double-flap, 5\u2032 flap, nicked duplex, and 3\u2032 overhang), whereas Pol I preferentially acted on DNA-only nicked and 3\u2032 overhang structures. These substrate preferences indicate that the major role of FEN is Okazaki fragment maturation while Pol I nuclease function is more important for DNA repair. As Pol I nuclease activity was not stimulated by concurrent DNA synthesis, we propose that in bacteria that encode a second, active FEN, RNA primers are primarily removed by FEN rather than Pol I. \n\nA more recent repair activity attributed to A-family polymerases, such as Pol I, is RNA-templated lesion bypass. As our FEN data suggest that the primary role of BsPol I is in DNA repair, we investigated whether Pol I could use ribonucleotides as a template for DNA synthesis. Since RNA is often found incorporated in DNA, either as part of R-patches or R-tracts, this category of damage represents a significant barrier to successful replication. We show that BsPol I performs efficient primer extension using both a template composed entirely of RNA or a DNA template containing embedded ribonucleotides. We also assayed other bacterial Pol Is and found that they possess similar capabilities as BsPol I, though the efficiency of this synthesis varies by species. This activity is not performed by the B. subtilis replicative polymerases, PolC and DnaE, as we found that neither are capable of sustained synthesis using a template that contains ribonucleotides. PolC was arrested by the inclusion of a single ribonucleotide in the template, while DnaE was able to synthesize DNA using a template that contained a stretch of 5 ribonucleotides. Together, these data support RNA-templated DNA synthesis by Pol I as a viable pathway for replication forks to navigate ribonucleotides incorporated in DNA.", "occurrence_notes":null, "guid":"145240-21896916@events.umich.edu", "permalink":"http:\/\/events.umich.edu\/event\/145240", "building_id":"1005169", "building_name":"Biological Sciences Building", "campus_maps_id":"631", "room":"1010", "location_name":"Biological Sciences Building", "has_livestream":0, "cost":"", "tags":["Biology","Bsbsigns","Dissertation","Dissertation Defense","seminar"], "website":"https:\/\/lsa.umich.edu\/mcdb\/news-events\/all-events.html#q=&filter=&start=&end=02\/09\/2027&tags=", "sponsors":[ { "group_name":"Department of Molecular, Cellular, and Developmental Biology", "group_id":"3755", "website":"" } ], "image_url":"https:\/\/events.umich.edu\/media\/attachments\/2026\/02\/event_145240_original-1.png", "styled_images":{ "event_thumb":"https:\/\/events.umich.edu\/media\/cache\/event_thumb\/media\/attachments\/2026\/02\/event_145240_original-1.png", "event_large":"https:\/\/events.umich.edu\/media\/cache\/event_large\/media\/attachments\/2026\/02\/event_145240_original-1.png", "event_large_2x":"https:\/\/events.umich.edu\/media\/cache\/event_large_2x\/media\/attachments\/2026\/02\/event_145240_original-1.png", "event_large_lightbox":"https:\/\/events.umich.edu\/media\/cache\/event_large_lightbox\/media\/attachments\/2026\/02\/event_145240_original-1.png", "group_thumb":"https:\/\/events.umich.edu\/media\/cache\/group_thumb\/media\/attachments\/2026\/02\/event_145240_original-1.png", "group_thumb_square":"https:\/\/events.umich.edu\/media\/cache\/group_thumb_square\/media\/attachments\/2026\/02\/event_145240_original-1.png", "group_large":"https:\/\/events.umich.edu\/media\/cache\/group_large\/media\/attachments\/2026\/02\/event_145240_original-1.png", "group_large_lightbox":"https:\/\/events.umich.edu\/media\/cache\/group_large_lightbox\/media\/attachments\/2026\/02\/event_145240_original-1.png", "event_large_crop":"https:\/\/events.umich.edu\/media\/cache\/event_large_crop\/media\/attachments\/2026\/02\/event_145240_original-1.png", "event_list":"https:\/\/events.umich.edu\/media\/cache\/event_list\/media\/attachments\/2026\/02\/event_145240_original-1.png", "event_list_2x":"https:\/\/events.umich.edu\/media\/cache\/event_list_2x\/media\/attachments\/2026\/02\/event_145240_original-1.png", "event_grid":"https:\/\/events.umich.edu\/media\/cache\/event_grid\/media\/attachments\/2026\/02\/event_145240_original-1.png", "event_grid_2x":"https:\/\/events.umich.edu\/media\/cache\/event_grid_2x\/media\/attachments\/2026\/02\/event_145240_original-1.png", "event_feature_large":"https:\/\/events.umich.edu\/media\/cache\/event_feature_large\/media\/attachments\/2026\/02\/event_145240_original-1.png", "event_feature_thumb":"https:\/\/events.umich.edu\/media\/cache\/event_feature_thumb\/media\/attachments\/2026\/02\/event_145240_original-1.png" }, "occurrence_count":1, "first_occurrence":21896916 } , "144206-21894841": { "datetime_modified":"20260312T123137", "datetime_start":"20260225T120000", "datetime_end":"20260225T130000", "has_end_time":1, "date_start":"2026-02-25", "date_end":"2026-02-25", "time_start":"12:00:00", "time_end":"13:00:00", "time_zone":"America\/Detroit", "event_title":"Resume Lab", "occurrence_title":"", "combined_title":"Resume Lab", "event_subtitle":"", "event_type":"Careers \/ Jobs", "event_type_id":"2", "description":"*RSVP required to attend. Click \"Join Event\" here:\u00a0https:\/\/umich.joinhandshake.com\/edu\/events\/1894075Just getting started building a resume? Have a draft but not sure how to make it better? Want to learn about resources available to revise your resume? Wherever you\u2019re at Resume Lab is a great next step for you.\u00a0Get real-time, personalized support in a small group setting by checking out the Resume Lab.\u00a0We will discuss and educate you on\u2026- Design and format- Writing a great bullet point- Targeting your resume for specific internships\/jobs\u00a0If you're a Graduate Student or Recent Grad, please make a 1:1 appointment instead of attending the Lab because this event is designed for undergraduates.\u00a0Note: This event's information is shown in Handshake as well as on theHappening @ Michigan calendar so that it will be seen by a larger number of U-M Students.#UCC", "occurrence_notes":null, "guid":"144206-21894841@events.umich.edu", "permalink":"http:\/\/events.umich.edu\/event\/144206", "building_id":"", "building_name":"", "campus_maps_id":"", "room":"", "location_name":"University Career Center, 3200 Student Activities Building, Program Room (3003), 515 E Jefferson St, Ann Arbor, MI, United States", "has_livestream":0, "cost":"", "tags":[], "website":"", "sponsors":[ { "group_name":"University Career Center UCC", "group_id":"1140", "website":"http:\/\/careercenter.umich.edu" } ], "image_url":"", "styled_images":{ "event_thumb":"", "event_large":"", "event_large_2x":"", "event_large_lightbox":"", "group_thumb":"", "group_thumb_square":"", "group_large":"", "group_large_lightbox":"", "event_large_crop":"", "event_list":"", "event_list_2x":"", "event_grid":"", "event_grid_2x":"", "event_feature_large":"", "event_feature_thumb":"" }, "occurrence_count":1, "first_occurrence":21894841 } }