an enzyme dna helicase unwinds or breaks

3E). As the DNA opens up, Y-shaped structures called replication forks are formed. unwinding is due to breakage of hydregen bonding of nitrogeneous bases. Is DNA a double helix? Epub 2006 Jun 5. For example, many RecQ helicases exhibit both DNA unwinding and annealing activities (19). How does helicase enzyme unwind strands of DNA? Where's helicase enzyme Can I still have hopes for an offer as a software developer. During the translation, it breaks the hydrogen bonds between the DNA-RNA hybrid. D, non-denaturing gel showing Pol-helicase unwinding of the indicated DNA substrate with a 5 ssDNA overhang. Pol-helicase unwinding may also enable microhomology annealing. Unable to load your collection due to an error, Unable to load your delegates due to an error. The other (antisense) strand must be moved out of the way for this to occur. By measuring the real-time motion of purified CMG unwinding DNA with magnetic tweezers, the authors reveal the . The unwinding and the separation of the strands are, um, inseparable from one another. 2022 Aug;204:348-360. doi: 10.1016/j.ymeth.2021.12.002. Non-denaturing gel showing Pol-helicase unwinding of the indicated DNA substrate with a 3 ssDNA overhang (right). Why do complex numbers lend themselves to rotation? 1C), and show that excess sequence-specific ssDNA trap is essential for detection of Pol-helicase unwinding (Fig. Read next:What Is DNA Ligase? Solved Match each enzyme or protein to its function during | Chegg.com How the eukaryotic helicase unzips DNA during replication is not well understood. The best answers are voted up and rise to the top, Not the answer you're looking for? @media(min-width:0px){#div-gpt-ad-geneticeducation_co_in-large-leaderboard-2-0-asloaded{max-width:300px!important;max-height:250px!important}}if(typeof ez_ad_units!='undefined'){ez_ad_units.push([[300,250],'geneticeducation_co_in-large-leaderboard-2','ezslot_7',192,'0','0'])};__ez_fad_position('div-gpt-ad-geneticeducation_co_in-large-leaderboard-2-0'); Read our article on prokaryotic DNA replication:Prokaryotic DNA replication. Does DNA polymerase I require a $3^\prime$ end? Vet Microbiol. Understanding the biochemical activities and cellular functions of Pol has become a priority because it has been found to be essential for the error-prone double-strand break (DSB)2 repair pathway known as microhomology-mediated end-joining (MMEJ) or alternative end-joining (alt-EJ) (3,9). Countering the Forcecage spell with reactions? 1 clearly show that Pol-helicase exhibits robust DNA unwinding activity that depends on hydrolysis of ATP or dATP. Recent studies of DNA and NTP binding and DNA unwinding by the Escherichia coli (E. coli) Rep helicase suggest that the Rep helicase dimer unwinds DNA by an active, rolling mechanism. 4C, RP470D/AO12/RP485. The strands must be separated so the incoming nucleotides for the newly fabricating strand can be base-paired to the template strand. ATP hydrolysis stimulates binding and release of single stranded DNA from alternating subunits of the dimeric E. coli Rep helicase: implications for ATP-driven helicase translocation. The human hexameric helicase has a central holo part in which the DNA binding motif is present. How Does a Helicase Unwind DNA? Insights from RecBCD Helicase One-Color vs Two-Color Microarray- How to Choose the Right One? sharing sensitive information, make sure youre on a federal The helicase is a class of the enzyme, especially, the DNA helicase that unwinds the dsDNA and facilitates, We are learning DNA replication and enzymes involved in DNA replication. The mechanism of DNA unwinding by the eukaryotic replicative helicase Helicase - Wikipedia The molecular weight of a DNA helicase is 300kDa. In the present article, we will discuss the structure and function of helicase and how different helicases are involved in the maintenance of the. 1A). In other places in the book, it says the function of helicase is to separate the two strands of DNA, and topoisomerase "relieves the supercoiling" caused by the strand separation activity of helicase. Epub 2021 Dec 8. Molecular mechanism of DNA replication - Khan Academy Alternatively, the helicase can potentially promote replication by facilitating strand displacement synthesis by the polymerase domain (Fig. Polymerase -helicase efficiently unwinds DNA and RNA-DNA hybrids Black line, DNA oligonucleotide. 1, C and D is that Pol-helicase actively translocates along ssDNA with a single polarity, but is capable of initiating unwinding at blunt or 3 recessed ends. Pol-helicase (residues 1894) was expressed and purified from Escherichia coli using a N-terminal tandem hexahistidine-SUMO tag which was subsequently cleaved (Fig. DNA helicase is an enzyme that unwinds DNA to allow for replication. For example, the substrates used in Fig. The results show that the helicase exclusively utilizes nucleotides containing adenine, but more efficiently unwinds DNA in the presence of ATP compared with dATP (Fig. Bio Chapter 22 DNA Flashcards | Quizlet Thus, Pol-helicase activity may be substantially stimulated by protein or DNA interactions that change the orientation of the autoinhibitory domain. The .gov means its official. *, identical residues; colon (:), residues sharing very similar properties; period (. @media(min-width:0px){#div-gpt-ad-geneticeducation_co_in-mobile-leaderboard-2-0-asloaded{max-width:250px!important;max-height:250px!important}}if(typeof ez_ad_units!='undefined'){ez_ad_units.push([[250,250],'geneticeducation_co_in-mobile-leaderboard-2','ezslot_15',190,'0','0'])};__ez_fad_position('div-gpt-ad-geneticeducation_co_in-mobile-leaderboard-2-0');In simple words, we can say that the helicase is a kind of rotating engine that move forward to perform its activity. DNA and RNA were 32P-5radiolabeled with T4 polynucleotide kinase (New England Biolabs) and [-32P]ATP (PerkinElmer Life Sciences). For example, although studies have shown that the helicase exhibits ATPase activity that is stimulated by ssDNA, multiple reports failed to detect a DNA unwinding function which is common among DNA helicases sharing sequence homology to Pol, such as HELQ/Hel308- and RecQ-type helicases (10, 16,18, 28, 33,35). Several helicases and their function are given into the table below. Solved choose the write answer An enzyme that unwinds the - Chegg Fig. Unwinding and Rewinding: Double Faces of Helicase? - Hindawi What does "Splitting the throttles" mean? also occurred which helps in separation of DNA-RNA duplex and allows transcription termination and regulates DNA replication. The oligomeric nature of helicases provides them with multiple DNA-binding sites, allowing the transient formation of ternary structures, such that at an unwinding fork, the helicase can bind either single-stranded and duplex DNA simultaneously or two strands of single-stranded DNA. government site. The results show that the polymerase possesses limited strand displacement activity in the presence of all four dNTPs and ATP as indicated by its inability to fully extend the leading strand primer (Fig. A unique feature of POLQ is that it is the only known gene in multicellular organisms to encode for a helicase and a polymerase. Accessibility Hence, these data suggest a plausible function for the helicase domain in facilitating Pol-polymerase strand displacement synthesis during replication repair. An official website of the United States government. Single-molecule visualization of stalled replication-fork rescue by the Escherichia coli Rep helicase. @media(min-width:0px){#div-gpt-ad-geneticeducation_co_in-leader-4-0-asloaded{max-width:300px!important;max-height:250px!important}}if(typeof ez_ad_units!='undefined'){ez_ad_units.push([[300,250],'geneticeducation_co_in-leader-4','ezslot_13',166,'0','0'])};__ez_fad_position('div-gpt-ad-geneticeducation_co_in-leader-4-0'); Several common motifs among different organism are enlisted below. 5B) (39). 6A). Once it starts spinning, it breaks the hydrogen bonds and moves forward, again, for another set of reaction, it utilizes another ATP. We are learning DNA replication and enzymes involved in DNA replication. What Is Helicase? And How It unwinds DNA? - Genetic Education Helicase and Topoisomerase are two enzymes that play essential roles in DNA replication.. Helicase is a motor protein that unwinds double-stranded DNA during replication by breaking the hydrogen bonds between base pairs. Interestingly, DNA helicase required a short stretch of the ssDNA for performing the unwinding during. @media(min-width:0px){#div-gpt-ad-geneticeducation_co_in-narrow-sky-1-0-asloaded{max-width:300px!important;max-height:250px!important}}if(typeof ez_ad_units!='undefined'){ez_ad_units.push([[300,250],'geneticeducation_co_in-narrow-sky-1','ezslot_17',186,'0','0'])};__ez_fad_position('div-gpt-ad-geneticeducation_co_in-narrow-sky-1-0');@media(min-width:0px){#div-gpt-ad-geneticeducation_co_in-narrow-sky-1-0_1-asloaded{max-width:300px!important;max-height:250px!important}}if(typeof ez_ad_units!='undefined'){ez_ad_units.push([[300,250],'geneticeducation_co_in-narrow-sky-1','ezslot_18',186,'0','1'])};__ez_fad_position('div-gpt-ad-geneticeducation_co_in-narrow-sky-1-0_1');.narrow-sky-1-multi-186{border:none!important;display:block!important;float:none!important;line-height:0;margin-bottom:7px!important;margin-left:auto!important;margin-right:auto!important;margin-top:7px!important;max-width:100%!important;min-height:250px;padding:0;text-align:center!important}Functions performed by the RNA helicase in RNA biogenesis are: It also facilitates the metabolism of nucleic acids by facilitating the ssNA (single-stranded nucleic acid). Here, we determined the efficiency of unwinding the 23-bp duplex substrate by relatively low amounts of either Pol-helicase, RPA, or both proteins combined. Indeed, here we demonstrate that by masking ssDNA annealing, we observe that Pol-helicase efficiently unwinds several different types of DNA substrates with 35 polarity, including replication forks, blunt-ended DNA, and DNA with 3 or 5 overhangs. (2016), Essential roles for polymerase -mediated end joining in the repair of chromosome breaks, Ceccaldi R., Liu J. C., Amunugama R., Hajdu I., Primack B., Petalcorin M. I. R., O'Connor K. W., Konstantinopoulos P. A., Elledge S. J., Boulton S. J., Yusufzai T., and D'Andrea A. D. (2015), Homologous-recombination-deficient tumours are dependent on Pol-mediated repair, Zelensky A. N., Schimmel J., Kool H., Kanaar R., and Tijsterman M. (2017), Inactivation of Pol and C-NHEJ eliminates off-target integration of exogenous DNA, van Kregten M., de Pater S., Romeijn R., van Schendel R., Hooykaas P. J., and Tijsterman M. (2016), T-DNA integration in plants results from polymerase--mediated DNA repair, Dual loss of human POLQ and LIG4 abolishes random integration, Polq-mediated end joining is essential for surviving DNA double-strand breaks during early zebrafish development, Fernandez-Vidal A., Guitton-Sert L., Cadoret J. C., Drac M., Schwob E., Baldacci G., Cazaux C., and Hoffmann J. S. (2014), A role for DNA polymerase in the timing of DNA replication, Seki M., Marini F., and Wood R. D. (2003), POLQ (Pol ), a DNA polymerase and DNA-dependent ATPase in human cells, Newman J. . Chapter 10 - DNA Replication Flashcards | Chegg.com But a consequence of the unwinding in the local region where the strands are being separated, is that other nearby regions get more tightly wound. J Mol Biol. official website and that any information you provide is encrypted 1C). This occurs because the DNA is far too long for the ends to spin around to accomodate this unwinding. For example, although some polymerases exhibit proficient strand displacement activity, which enables DNA unwinding downstream of the 3 primer terminus during replication, many polymerases such as those involved in chromosomal replication require the unwinding activity of auxiliary helicases to perform replication of double strand DNA. Helicase breaks the hydrogen bonds forming the double helix structure of DNA. Furthermore, the helicase provides the strand migration or exchange of genetic material during the process of recombination. (2017), The helicase domain of Pol counteracts RPA to promote alt-NHEJ, Sollier J., Stork C. T., Garca-Rubio M. L., Paulsen R. D., Aguilera A., and Cimprich K. A. If you would like to change your settings or withdraw consent at any time, the link to do so is in our privacy policy accessible from our home page.. Escherichia coli rep helicase unwinds DNA by an active mechanism. MeSH Why wouldn't the replication complex just rotate (spiral) along the double helix? 32P-5radiolabeled DNA pre-incubated at room temperature in 25 mm Tris-HCl, pH 8.8, 1 mm DTT, 0.01% Nonidet P-40, 0.1 mg/ml BSA, 10% glycerol, 10 mm MgCl2 was mixed with or without 50 nm Pol-helicase. Before FOIA Pol-polymerase was added for an additional 20 min in a total volume of 20 l. Fig. It runs ahead of the replication fork and continuously unwinds the dsDNA, providing the template for DNA polymerase to work. Helicases are a class of enzymes that all perform the same function during DNA replication. The catalytic activity of DNA helicase starts with recognising the dsDNA strand. Next, 2 mm ATP and 20 m dNTPs were added along with 400 nm unlabeled ssDNA trap for 30 min at 30 C. For instance, a prior report demonstrated that domain 5 within Hel308 suppresses its unwinding activity (35). Processivity of nucleic acid unwinding and translocation by helicases. For example, prior studies showed that mammalian HELQ/Hel308 is recruited to stalled replication forks and is involved in repairing interstrand cross-links which arrest replication forks (28, 37, 38). Failure of Pol-helicase to unwind a RNA-DNA substrate containing a 3 RNA overhang indicates that this enzyme exclusively translocates along ssDNA (Fig. Recently, increasing evidence demonstrates that some helicases also possess rewinding activityin other words, they can anneal two complementary single-stranded nucleic acids. R01 GM045948/GM/NIGMS NIH HHS/United States. Pol-helicase, Pol-polymerase, and RPA were purified as described (20). government site. DNA helicases are a class of molecular motors that catalyze processive unwinding of double stranded DNA. DNA helicase is an ATP dependent catalytic enzyme which unwinds the dsDNA for providing leading as well as lagging strand replication. 32P-5radiolabeled DNA, RNA-DNA, or RNA templates were preincubated at room temperature in buffer (25 mm Hepes-NaOH, pH 7.0, 2 mm DTT, 0.01% Nonidet P-40, 40 mm KCl, 5% glycerol, 1 mm MgCl2) then mixed with the indicated amounts of Pol-helicase for 5 min. Introduction POLQ is a unique gene in higher eukaryotes that encodes for a N-terminal superfamily 2 (SF2) helicase and a C-terminal A-family polymerase with a large central domain that lacks any known enzymatic domain ( Fig. A, sequence alignment of motifs IVaVI of Pol/Hel308/Ski2-related SF2 helicases. Remarkably, Pol expression has also been shown to be important for the proliferation of cells deficient in the homologous recombination (HR) pathway, such as because of mutations in BRCA1 or BRCA2 (4, 10). The heilcase unwinding is merely straightening out the double helix in a very local area. It folds the DNA into a coiled structure. 3C, RP469R/RP469DC. Multiple studies have reported that polymerase -helicase (Pol-helicase) is unable to unwind DNA. Nonetheless, how the helicase starts unwinding the dsDNA, in vivo (during replication) is still not known. Polymerase -helicase efficiently unwinds DNA and RNA-DNA hybrids Elife. rev2023.7.7.43526. Nevertheless, we proceeded to determine which nucleotide cofactors support the enzyme's unwinding activity. Morse theory on outer space via the lengths of finitely many conjugacy classes. Methods. Thus, although Pol has an essential role in alt-EJ, additional lines of evidence suggest it might exhibit separate functions in response to replicative stress, such as replication fork restart (10). https://en.wikipedia.org/wiki/Topoisomerase. S1C). The results show that the addition of both proteins results in synergistic activity which is indicated by a significantly higher yield of unwound DNA (Fig. This report also shows that knockdown of Pol expression impairs fork progression and halts cells in S-phase following hydroxyurea treatment (10). (2013), RECQL5 plays co-operative and complementary roles with WRN syndrome helicase, Hu Y., Raynard S., Sehorn M. G., Lu X., Bussen W., Zheng L., Stark J. M., Barnes E. L., Chi P., Janscak P., Jasin M., Vogel H., Sung P., and Luo G. (2007), RECQL5/Recql5 helicase regulates homologous recombination and suppresses tumor formation via disruption of Rad51 presynaptic filaments, SWISS-MODEL and the Swiss-PdbViewer: An environment for comparative protein modeling, Unraveling hot spots in binding interfaces: Progress and challenges, Li W., Cowley A., Uludag M., Gur T., McWilliam H., Squizzato S., Park Y. M., Buso N., and Lopez R. (2015), The EMBL-EBI bioinformatics web and programmatic tools framework, supp_RA117.000565_133344_1_supp_71683_p3ssx4.pdf, supp_RA117.000565_133344_1_supp_70555_p3qvx8.pdf, https://www.ebi.ac.uk/Tools/msa/clustalo/. Different motif present in the core of the enzyme helps in processing the ATP. It breaks the hydrogen bonds that hold the two strands of the DNA together. A. Y. O., T. R., T. K., and L. A. S. data curation; A. Y. O. investigation; A. Y. O., T. R., and T. K. methodology; R. T. P. conceptualization; R. T. P. supervision; R. T. P. funding acquisition; R. T. P. writing-original draft; R. T. P. project administration. Helicase is an enzyme vital for the initiation of DNA replication. *, 32P. Unauthorized use of these marks is strictly prohibited. The ATP converts into ADP and releases the energy which is utilized to activate the jet engine of helicase. Mersch KN, Sokoloski JE, Nguyen B, Galletto R, Lohman TM. The results clearly show that the helicase preferentially unwinds the fork containing the lagging strand but lacking the leading strand (Fig. E and F, non-denaturing gels showing Pol-helicase DNA unwinding in the presence of the indicated nucleotides. Escherichia coli DNA helicases: mechanisms of DNA unwinding and transmitted securely. Despite these initial findings, the biochemical and cellular functions of Pol-helicase have yet to be fully elucidated. and transmitted securely. ATP hydrolysis is required for this process. Polymerase -helicase efficiently unwinds DNA and RNA-DNA hybrids Helicase unwinds the DNA Helicases are enzymes that bind and may even remodel nucleic acid or nucleic acid protein complexes. Denaturation step during the PCR reaction replaces the requirement of helicase during in vitro DNA amplification. Because Pol is known to promote the proliferation of BRCA-deficient cancer cells and is considered a promising oncology drug target, it will be important to determine whether the unwinding function of the helicase domain contributes to cancer cell survival (4, 10). https://en.wikipedia.org/wiki/Topoisomerase, Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood. 1D and and22C, RP469D/RP484. Further to this, we had already discussed the function and structure of DNA primase that provides RNA primer for starting DNA replication. in making a new double helix, DNA replication uses, or conserves one parental DNA strand and synthesizes one new strand. 2G). An official website of the United States government. Interestingly, other SF2 helicases, such as those from the RecQ subclass, exhibit ssDNA annealing, however, in many cases this activity is suppressed by ATP (19). Mg2+ for H-bonds and co-factory for enzymes; DNA polymerase . 3D). 1A) (16). Dr Tushar Chauhan is a Scientist, Scientific-writer and co-founder of Genetic Education. Clipboard, Search History, and several other advanced features are temporarily unavailable. Several lines of evidence have supported a role for Pol in replication fork repair. Figure 1: Helicase (yellow) unwinds the double helix. In DNA replication, the helicase works by creating a complex with other proteins such as DNA primase, polymerase or single stranded-binding proteins. Because Pol-polymerase exhibits poor strand displacement synthesis, DNA unwinding ahead of the polymerase would be a plausible function for the helicase during alt-EJ (Fig. Explanation: DNA helicase is used to unwind the dna strand i.e. Read our DNA replication article: General process of DNA replication. 6 Types of Microarray-based Genetic Testing. Please enable it to take advantage of the complete set of features! . Breaking of hydrogen bonds take place during DNA replication but it may also take place in high temperature ( denaturation ). The authors declare that they have no conflicts of interest with the contents of this article. Before Time courses of Pol-helicase unwinding were performed on replication forks containing leading or lagging strands, leading and lagging strands, or a fork lacking leading and lagging strands (Fig. Synthesizes short stretches of RNA that are complementary to the DNA so that DNA polymerase has a starting point. Inclusion in an NLM database does not imply endorsement of, or agreement with, Some of the diseases in which the helicase is involved are Blooms syndrome, alpha-thalassemia, xeroderma pigmentation and Cockayne syndrome. Once the DNA entred into the holo part, the motifs Walker A and Walker B starts hydrolysis of ATP and release energy to break the hydrogen bond. The C-bound form of Hel308 (PDB ID: 2P6R) was used as reference onto which the Pol-helicase domain (PDB ID: 5AGA) was superimposed using Swiss-PdbViewer (42). 1B) (20). Sequence and structural comparison of Pol-helicase and HELQ/Hel308 enzymes. Guo B, Jin X, Chen J, Xu H, Zhang M, Lu X, Wu R, Zhao Y, Guo Y, An Y, Li S. Genes (Basel). 3E, RP469R/RP470R. It acts as a molecular motor that uses ATP hydrolysis to move along the DNA strand and separate the two strands, allowing them to be . Assume that, the RNA primer is ready for starting the replication, now a single-stranded DNA is needed for primer binding. For instance, detection of DNA unwinding by Pol-helicase requires masking the opposite annealing activity by addition of excess ssDNA trap. At each replication fork, DNA helicase unwinds the DNA and topisomerase alleviates positive supercoiling. Indeed, using identical substrate sequences, our results show that RNA-DNA substrates are also efficiently unwound by Pol-helicase (Fig. What is the breaking of the hydrogen bonds that hold the two - Socratic Although the activities and cellular functions of Pol-polymerase have been investigated, little is understood regarding the enzymatic activities of Pol-helicase. Nonetheless, how the helicase starts unwinding the dsDNA. 5). The initiation of DNA replication occurs in two steps. Another similar function between Pol-helicase and RECQL5 is their ability to interact with RAD51 and counteract its activity. For example, in recent studies we found that Pol-helicase exhibits DNA annealing activity, similar to RecQ-type helicases (20). % unwinding is indicated. For example, a recent report demonstrated that suppression of Pol significantly slows the velocity of replication forks even in the absence of exogenous DNA damaging agents (10). In contrast, HELQ/Hel308 has been shown to unwind DNA in the absence of a ssDNA trap and therefore does not likely exhibit strong annealing activity like Pol-helicase (28). Kinetic and structural mechanism for DNA unwinding by a non-hexameric helicase. Fig. Modulation of the relative affinities of these binding sites for single-stranded versus duplex DNA through ATP binding and hydrolysis would then provide the basis for a cycling mechanism for processive unwinding of DNA by helicases. B, superposition of Pol-helicase (green) (PDB ID: 5AGA) and Hel308 in complex with DNA (blue) (PDB ID: 2P6R) highlighting the -hairpin motif. Different maturities but same tenor to obtain the yield. Multiple studies have reported that polymerase -helicase (Pol-helicase) is unable to unwind DNA. DNA helicases are a class of molecular motors that catalyze processive unwinding of double stranded DNA. Disclaimer. In addition to these functions, Pol was shown to be essential for DSB repair in zebrafish embryos and is involved in replication timing and potentially replication fork repair (10, 14, 15). The topoisomerase alleviates this stressful coiling. Cells Can Replicate Their DNA Precisely - Nature This suggests that multiple Pol-helicase molecules are unable to act cooperatively to unwind long substrates, as indicated for SF1-type helicase UvrD (22). @media(min-width:0px){#div-gpt-ad-geneticeducation_co_in-medrectangle-4-0-asloaded{max-width:300px!important;max-height:250px!important}}if(typeof ez_ad_units!='undefined'){ez_ad_units.push([[300,250],'geneticeducation_co_in-medrectangle-4','ezslot_6',141,'0','0'])};__ez_fad_position('div-gpt-ad-geneticeducation_co_in-medrectangle-4-0');DNA helicase unzips the dsDNA to continue DNA replication. doi: 10.7554/eLife.77483. When practicing scales, is it fine to learn by reading off a scale book instead of concentrating on my keyboard? Genetics Chapter 9 Flashcards | Quizlet 2A). This separates the strands such that one strand can serve as a template for transcription or replication. Conserved arginines are represented as sticks. 1996;65:169-214. doi: 10.1146/annurev.bi.65.070196.001125. Taken together, Pol-helicase shares similar characteristics with RECQL5 and HELQ/Hel308. 4B, Leading strand fork, RP470D/AO12/AO18; Lagging strand fork, RP470D/AO17/AO19. WHAT are the steps of replication? 1995 Apr;68(4 Suppl):180S-184S; discussion 184S-185S. doi: 10.1073/pnas.2216777120. Proc Natl Acad Sci U S A. MeSH Non-denaturing gel showing the lack of Pol-helicase K121M DNA unwinding (right). Pol-helicase also efficiently unwinds RNA-DNA hybrids and exhibits a preference for unwinding the lagging strand at replication forks, similar to related HELQ helicase. J Mol Biol. How does the helicase enzyme break the hydrogen bonds between the strands of DNA? REPLICATION Flashcards | Chegg.com
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