Directional Resolution of Synthetic Holliday Structures by the Cre Recombinase

The Cre recombinase of bacteriophage P1 cleaves its target site, loxP, in a defined order. Recombination is initiated on one pair of strands to form a Holliday intermediate, which is then resolved by cleavage and exchange of the other pair of strands to yield recombinant products. To investigate the influence of the loxP sequence on the directionality of resolution, we constructed synthetic Holliday (χ) structures containing either wild-type or mutant lox sites. We found that Cre preferentially resolved the synthetic wild-type χ structures on a particular pair of strands. The bias in the direction of resolution was dictated by the asymmetric loxPsequence since the resolution bias was abolished with symmetriclox sites. Systematic substitutions of the loxPsite revealed that the bases immediately 5′ to the scissile phosphodiester bonds were primarily responsible for the directionality of resolution. Interchanging these base pairs was sufficient to reverse the resolution bias. The Cre-lox co-crystal structures show that Lys86 makes a base-specific contact with guanine immediately 5′ to one of the scissile phosphates. Substituting Lys86 with alanine resulted in a reduction of the resolution bias, indicating that this amino acid is important for establishing the bias in resolution. The Cre recombinase of bacteriophage P1 cleaves its target site, loxP, in a defined order. Recombination is initiated on one pair of strands to form a Holliday intermediate, which is then resolved by cleavage and exchange of the other pair of strands to yield recombinant products. To investigate the influence of the loxP sequence on the directionality of resolution, we constructed synthetic Holliday (χ) structures containing either wild-type or mutant lox sites. We found that Cre preferentially resolved the synthetic wild-type χ structures on a particular pair of strands. The bias in the direction of resolution was dictated by the asymmetric loxPsequence since the resolution bias was abolished with symmetriclox sites. Systematic substitutions of the loxPsite revealed that the bases immediately 5′ to the scissile phosphodiester bonds were primarily responsible for the directionality of resolution. Interchanging these base pairs was sufficient to reverse the resolution bias. The Cre-lox co-crystal structures show that Lys86 makes a base-specific contact with guanine immediately 5′ to one of the scissile phosphates. Substituting Lys86 with alanine resulted in a reduction of the resolution bias, indicating that this amino acid is important for establishing the bias in resolution. base pair(s) nucleotide(s) The Cre recombinase of bacteriophage P1 belongs to the integrase family of conservative site-specific recombinases whose members include the integrase of bacteriophage λ (1Landy A. Ann. Rev. Biochem. 1989; 58: 913-949Crossref PubMed Google Scholar), XerC/XerD of Escherichia coli (2Sherratt D.J. Arciszewska L.K. Blakely G. Colloms S. Grant K. Leslie N. McCulloch R. Philos. Trans. R. Soc. Lond. Ser. B Biol. Sci. 1995; 347: 37-42Crossref PubMed Scopus (97) Google Scholar), and the Flp protein of the 2µm plasmid (3Sadowski P.D. Prog. Nucleic Acid Res. Mol. Biol. 1995; 51: 53-91Crossref PubMed Scopus (125) Google Scholar). Cre assists in the efficient segregation of the low copy P1 plasmid during bacterial cell division by resolving dimeric lysogenic P1 plasmids into monomeric units (4Austin S. Ziese M. Sternberg N. Cell. 1981; 25: 729-736Abstract Full Text PDF PubMed Scopus (218) Google Scholar). Cre breaks and rejoins DNA at specific sequences called theloxP sites (Fig.1 a). The 34-bp1 loxP site is composed of two 13-bp symmetry elements surrounding an 8-bp asymmetric AT-rich region (5Hoess R.H. Ziese M. Sternberg N. Proc. Natl. Acad. Sci. U. S. A. 1982; 79: 3398-3402Crossref PubMed Scopus (234) Google Scholar). Since the symmetry elements inloxP have identical sequences, the orientation of theloxP site is dictated by the asymmetric central region. A 6-bp overlap region separates the two cleavage sites. This organization of the recombination site is common to the integrase family members, although the interval of the overlap region varies (1Landy A. Ann. Rev. Biochem. 1989; 58: 913-949Crossref PubMed Google Scholar, 2Sherratt D.J. Arciszewska L.K. Blakely G. Colloms S. Grant K. Leslie N. McCulloch R. Philos. Trans. R. Soc. Lond. Ser. B Biol. Sci. 1995; 347: 37-42Crossref PubMed Scopus (97) Google Scholar, 3Sadowski P.D. Prog. Nucleic Acid Res. Mol. Biol. 1995; 51: 53-91Crossref PubMed Scopus (125) Google Scholar). Certain recombinases such as λ-integrase and XerC/XerD have additional accessory sequences and require accessory protein factors (1Landy A. Ann. Rev. Biochem. 1989; 58: 913-949Crossref PubMed Google Scholar, 6Colloms S.D. McCulloch R. Grant K. Neilson L. Sherratt D.J. EMBO J. 1996; 15: 1172-1181Crossref PubMed Scopus (114) Google Scholar). The integrase family members share a common mechanism of catalysis that involves the formation of a four-way branched DNA intermediate known as a Holliday junction (7Holliday R. Genet. Res. 1964; 5: 282-304Crossref Scopus (1256) Google Scholar, 8Hoess R. Wierzbicki A. Abremski K. Proc. Natl. Acad. Sci. U. S. A. 1987; 84: 6840-6844Crossref PubMed Scopus (131) Google Scholar, 9Nunes-Düby S. Matsumoto L. Landy A. Cell. 1987; 50: 779-788Abstract Full Text PDF PubMed Scopus (185) Google Scholar, 10Kitts P.A. Nash H.A. Nucleic Acids Res. 1988; 16: 6839-6856Crossref PubMed Scopus (47) Google Scholar, 11Meyer-Leon L. Huang L.C. Umlauf S.W. Cox M.M. Inman R.B. Mol. Cell. Biol. 1988; 8: 3784-3796Crossref PubMed Scopus (43) Google Scholar, 12Jayaram M. Crain K.L. Parsons R.L. Harshey R.M. Proc. Natl. Acad. Sci. U. S. A. 1988; 85: 7902-7906Crossref PubMed Scopus (58) Google Scholar, 13Arciszewska L.K. Sherratt D.J. EMBO J. 1995; 14: 2112-2120Crossref PubMed Scopus (72) Google Scholar). Formation and resolution of the Holliday intermediate occur via two sequential sets of single-strand DNA cleavages and exchanges (Fig. 1 b). DNA cleavage is mediated by a tyrosine residue that is absolutely conserved among the integrase family members, and hence, members of this family are also known as tyrosine recombinases (14Argos P. Landy A. Abremski K. Egan J.B. Haggard-Ljungquist E. Hoess R.H. Kahn M.L. Kalionis B. Narayana S.V. Pierson III, L.S. Sternberg N. Leong J.M. EMBO J. 1986; 5: 433-440Crossref PubMed Scopus (374) Google Scholar, 15Wierzbicki A. Kendall M. Abremski K. Hoess R. J. Mol. Biol. 1987; 195: 785-794Crossref PubMed Scopus (65) Google Scholar, 16Nunes-Düby S.E. Kwon H.J. Tirumalai R.S. Ellenberger T. Landy A. Nucleic Acids Res. 1998; 26: 391-406Crossref PubMed Scopus (363) Google Scholar). The catalytic tyrosine makes a nucleophilic attack upon the scissile phosphodiester bond, resulting in the covalent attachment of the protein via a 3′-phosphotyrosine linkage and the release of a free 5′-hydroxyl DNA end. The phosphotyrosine bond is thought to conserve the energy of the scissile phosphodiester bond. The cleaved strands from two loxP sites involved in the recombination are exchanged and ligated, resulting in the formation of a Holliday junction. The Holliday intermediate is then resolved by a second set of strand cleavages and exchanges. Depending on which pair of strands is cleaved, the Holliday intermediate may be resolved to either the parental or the recombinant configuration. Several tyrosine recombinases such as the λ-integrase, XerC/XerD, and Cre proteins catalyze recombination with a defined order of strand exchange in which one pair of strands is preferentially cleaved and exchanged first (6Colloms S.D. McCulloch R. Grant K. Neilson L. Sherratt D.J. EMBO J. 1996; 15: 1172-1181Crossref PubMed Scopus (114) Google Scholar, 8Hoess R. Wierzbicki A. Abremski K. Proc. Natl. Acad. Sci. U. S. A. 1987; 84: 6840-6844Crossref PubMed Scopus (131) Google Scholar, 9Nunes-Düby S. Matsumoto L. Landy A. Cell. 1987; 50: 779-788Abstract Full Text PDF PubMed Scopus (185) Google Scholar, 10Kitts P.A. Nash H.A. Nucleic Acids Res. 1988; 16: 6839-6856Crossref PubMed Scopus (47) Google Scholar, 13Arciszewska L.K. Sherratt D.J. EMBO J. 1995; 14: 2112-2120Crossref PubMed Scopus (72) Google Scholar, 17Kitts P.A. Nash H.A. Nature. 1987; 329: 346-348Crossref PubMed Scopus (127) Google Scholar, 18Kitts P.A. Nash H.A. J. Mol. Biol. 1988; 204: 95-107Crossref PubMed Scopus (73) Google Scholar). Hoess et al. (8Hoess R. Wierzbicki A. Abremski K. Proc. Natl. Acad. Sci. U. S. A. 1987; 84: 6840-6844Crossref PubMed Scopus (131) Google Scholar, 19Hoess R.H. Wierzbicki A. Abremski K. Sarma R.H. Sarma M.H. Structure & Methods Vol. 1: Human Genome Initiative & DNA. Adenine Press, Guilderland, NY1990: 203-213Google Scholar) isolated the α Holliday intermediate formed during a The strands strand is defined as the strand with the cleavage site the at and strand is defined as the strand with the cleavage site the at and of theloxP sites exchanged in these Holliday that Cre initiated recombination on the strands. The α was preferentially resolved on the strands to yield recombinant (8Hoess R. Wierzbicki A. Abremski K. Proc. Natl. Acad. Sci. U. S. A. 1987; 84: 6840-6844Crossref PubMed Scopus (131) Google Scholar). The order of strand exchange was by on the of in the loxP overlap region on and G. 1998; PubMed Scopus Google Scholar) found that the strand cleavage site and (Fig. 1 was for the formation of the Holliday intermediate, the cleavage site to was for resolution. Cre to strand cleavage and exchange on the strands to a Holliday and the Holliday intermediate is resolved on the strands to yield recombinant products. A the tyrosine recombinase family is are the factors that the order of strand exchange and the directionality of resolution of the Holliday the central are the asymmetric of the we the influence of this asymmetric sequence on the directionality of resolution of synthetic Holliday (χ) We synthetic χ structures containing either wild-type or sites. We found that Cre preferentially resolved the wild-type χ structures on the strands. This bias was dictated by the asymmetric loxP in particular by the bases immediately 5′ to the scissile phosphodiester bonds and We found that which the of guanine at Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar), was important for establishing the resolution bias of the Cre χ was constructed from a and The were by and were by on a from the by the J. T. A Scholar), the were by on a to the wild-type Holliday to loxP sequences are in with the central 8-bp sequence in and the sequences the loxP sites are in The loxP sequences are in with the central 8-bp sequence in and the sequences the loxP sites are in in a of χ structures by wild-type Cre and Cre 8-bp sequences of the symmetry elements and the of the mutant χ structures are the as the central 8-bp lox sequences for the mutant χ structures are from sequences that from wild-type are in and the are 1 and of the χ the sequences in the strands and that in the resolution bias is as the of the of to resolution from The of resolution in the was a and for in the Cre protein wild-type Cre mutant protein an The wild-type Cre protein the resolution bias as the wild-type Cre indicating that the influence the direction of resolution (Fig. and The sequences of the symmetry elements and the of the mutant χ structures are the as the central 8-bp lox sequences for the mutant χ structures are from sequences that from wild-type are in and the are 1 and of the χ the sequences in the strands and that in the The resolution bias is as the of the of to resolution from The of resolution in the was a and for in the Cre protein wild-type The Cre mutant protein an The wild-type Cre protein the resolution bias as the wild-type Cre indicating that the influence the direction of resolution (Fig. and in a 1 of χ was with to the and a). strand was of strand 1 to the and resolution products. The that a particular χ were by to and in and The were in the in a of χ was with Cre in and DNA at for 1 by which the were by with and at for The resolution were on a of the resolution was on a to the of the products. The in the on the was a The of resolution was as the in the by the in the and A was from the Cre The resolution bias is as the of the of to The Cre mutant protein was constructed with a at the for of the the wild-type to a in a P.D. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). Lys86 of was to alanine by the to the of are in the is and the site is in are in the is and the site is in and to sequences amino The was in as by R. A to Methods and Press, Scholar). The was with and into to form the and the of were by DNA and were by the for at the of and were by The DNA in the was from The and DNA were from The to the was from U. S. Cre and were from and constructed by and P.D. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar), was from was in E. coli as by and P.D. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). The wild-type wild-type and proteins were as by and P.D. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). on that the proteins were was the M.M. Biochem. PubMed Scopus Google Scholar) with as the protein The proteins were at To investigate the resolution of the Holliday by the Cre we constructed synthetic Holliday (χ) structures containing two loxP sites a). The DNA to the wild-type are in and a of the central 8-bp region of the loxP sites at the Holliday junction is in the of strands 1 and to the strands of theloxP site, strands and to the strands. The loxP sites in the synthetic χ are by of sequences in the to the loxP sites. The are of that the direction of resolution be from the of the resolution products. resolution by cleavage of strands 1 and the and products. on strands and the and products. of the χ with two that with and DNA (Fig. the and resolution are on the strand 1 of the χ was at its The other resolution and be strand was The of the resolution and the cleaved were by on We found that Cre preferentially resolved the wild-type on the strands of of the strand resolution was formed the strand resolution The bias resolution on the strands was in the strand was to the resolution the other strand resolution by also The resolution that we for synthetic was by Hoess et al. (8Hoess R. Wierzbicki A. Abremski K. Proc. Natl. Acad. Sci. U. S. A. 1987; 84: 6840-6844Crossref PubMed Scopus (131) Google Scholar). isolated a Holliday intermediate that was by Cre mutant proteins during an in recombination with a pair with synthetic an for resolution of the α on the strands of theloxP sites the strands. the of the α was cleaved to an χ Hoess et al. resolution of the χ This from with the synthetic A for the is that the sequences the loxP sites may have the direction of resolution. synthetic is and sequences with the χ by Hoess et al. To the sequences in the of synthetic χ were responsible for the resolution, we constructed the in which the orientation of the loxP sites is to the sequences the as in The wild-type loxP strands 1 and to the strands and are the strands. the resolution bias was by theloxP we that the orientation of the loxP sites reverse the bias. the other the sequences were primarily responsible for the resolution bias, the loxP orientation the We found that Cre preferentially resolved the on the the and the we that for synthetic χ the bias in the direction of resolution was dictated by the sequences in the we the that the sequences in the of the χ or other factors be responsible for the resolution by Hoess et al. (8Hoess R. Wierzbicki A. Abremski K. Proc. Natl. Acad. Sci. U. S. A. 1987; 84: 6840-6844Crossref PubMed Scopus (131) Google Scholar) the central 8-bp sequence is the asymmetric of the loxP site, we this asymmetric sequence the direction of resolution. We constructed synthetic χ structures containing sequences in the central 8-bp the sequences in the as The for the resolution of these χ structures are in and the resolution as the are in The and structures lox sites to either the or of the wild-type loxP site, Cre resolved these bias, a of to 1 (Fig. and This that the sequence is responsible for the bias in the direction of resolution. To the sequences the loxP central region responsible for the bias in the direction of resolution, we first on and surrounding the scissile phosphates. the wild-type loxP site, an the cleavage site and a the cleavage site and the at these were in the the direction of resolution was (Fig. of the resolution bias was abolished we either a (Fig. or an at cleavage although a strand bias. The Cre-lox co-crystal structures show that the the 6-bp overlap region are base-specific Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, Nature. PubMed Scopus Google EMBO J. 1998; PubMed Scopus Google Scholar). the other the immediately 5′ to the scissile and to be involved in an asymmetric contact with Lys86 Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). and G. 1998; PubMed Scopus Google Scholar) found that these base pairs of the asymmetric region are important for We in the sequences at these two the direction of resolution. Interchanging the base pair at and the base pair at in the the resolution bias (Fig. The resolution bias was was either a guanine (Fig. or an at and although a strand bias. we substitutions at and and found that Cre preferentially resolved to an A a at these We a at the the directionality of resolution. To this we substitutions at these The χ structures are the to the and the base to the base 5′ to the scissile a to the cleavage This was resolved in either direction (Fig. the strand bias of and the resolution of that resolution at is This was for in which a the strand bias to a (Fig. with A also resulted in a strand bias (Fig. that resolution at is at This was the for which bias the strand (Fig. and that Cre to the resolution for the base that is immediately 5′ to the scissile A T. The in the lox region the resolution bias, also the of resolution products. is a of the of and that at of the mutant χ structures were resolved at a with wild-type and the and structures were resolved wild-type and and a at and and is that the at these cleavage The structures of Cre to a symmetriclox site the lox sequence as in the that Lys86 bonds to the of at and in the Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). et al. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar) that in the site, Lys86 a base-specific contact with at with A at which an amino To investigate this asymmetric contact of Lys86 is involved in the direction of resolution, we Lys86 to alanine The Cre mutant protein was constructed with a at the for of The the and of recombination by wild-type Cre to wild-type Cre The wild-type Cre protein resolution bias with the wild-type Cre protein indicating that the influence the direction of resolution. The Cre protein resolved the synthetic χ structures on the wild-type Cre protein (Fig. Cre is in to the loxP site, is in recombination by to wild-type and P. The also the directionality of resolution. A of the resolution bias of the χ structures by wild-type and Cre proteins is in The Cre protein or bias in the resolution of the wild-type and The also or abolished of the bias in the resolution of and for these χ Lys86 to be for the bias in resolution. the to the bias in the resolution of the The mutant protein also bias with the wild-type protein in the resolution of and the a bias the strands in the resolution of the and the wild-type protein bias. the of the χ structures in this the Cre protein a bias in the direction of resolution of or The are and Cre a for resolving to a the to the of Cre to and at and the for a residue the other bases The Cre protein and other tyrosine recombinases catalyze site-specific recombination via a Holliday We have in this that Cre preferentially synthetic χ structures on the strands of the loxP sites. The bias in the direction of resolution is dictated by the in particular the bases at and which is known from the Cre-lox co-crystal structures to contact the guanine at Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, Nature. PubMed Scopus Google Scholar, EMBO J. 1998; PubMed Scopus Google Scholar), is important for establishing the resolution bias by the Cre Hoess et al. (8Hoess R. Wierzbicki A. Abremski K. Proc. Natl. Acad. Sci. U. S. A. 1987; 84: 6840-6844Crossref PubMed Scopus (131) Google Scholar) also a strand resolution bias, in the of an α The α is a Holliday intermediate in which two of the form a Hoess et al. isolated the α formed during a recombination two sites on a pair the α was to an χ by found that the bias in resolution was DNA to influence the directionality of resolution of Holliday by E. coli and bacteriophage Colloms S.D. Sherratt D.J. J. Mol. Biol. PubMed Scopus Google Scholar). that the loxP sequence also to resolution of Holliday by factors may have the strand bias during the resolution of the χ of Hoess et al. (8Hoess R. Wierzbicki A. Abremski K. Proc. Natl. Acad. Sci. U. S. A. 1987; 84: 6840-6844Crossref PubMed Scopus (131) Google Scholar). we have that the sequences the loxP sites to the directionality of resolution of synthetic χ the and of the χ by Hoess et al. may have to the resolution bias. into the sequences may have responsible for the of resolution bias. The loxP sites in the in the resolution by Hoess et on either of the loxP sites K. Hoess R. Sternberg N. Cell. Full Text PDF PubMed Scopus Google Scholar), and the Holliday junction be to the in the χ be to the loxP sites in synthetic χ Since Cre strand cleavage on the strands of theloxP site (8Hoess R. Wierzbicki A. Abremski K. Proc. Natl. Acad. Sci. U. S. A. 1987; 84: 6840-6844Crossref PubMed Scopus (131) Google Scholar, 19Hoess R.H. Wierzbicki A. Abremski K. Sarma R.H. Sarma M.H. Structure & Methods Vol. 1: Human Genome Initiative & DNA. Adenine Press, Guilderland, NY1990: 203-213Google Scholar), resolution on the strand is with the order of strand exchange to recombinant products. the resolution bias be to the that cleavage on the strands is efficient on the strands. The and structures were resolved the other χ and a at and that the at and at the cleavage sites of may al. G. J. T. M. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar) that cleavage on the strand of the loxP is efficient cleavage on the We have also a cleavage on the and strands to the covalent The direction of resolution is dictated by the asymmetric loxP The resolution bias was abolished the Holliday loxP sites. the direction of resolution was primarily by the base pairs at and and are 5′ to the scissile to which Cre via a 3′-phosphotyrosine bond upon strand of and revealed that Cre the resolution for the base that is immediately 5′ to the scissile A T. and G. 1998; PubMed Scopus Google Scholar) found that substitutions at or of the loxP site recombination and that these may be involved in the order of strand found that Cre and containing the site as and P. and G. 1998; PubMed Scopus Google Scholar) this particular mutant lox we have the first cleavage in this we found that substitutions at the resolution bias. the yield of resolution products. the low recombination by and may have to in the first cleavage to the of the first strand exchange to parental products. The base pairs immediately 5′ to the cleavage sites may also influence the directionality of resolution for other tyrosine The λ-integrase strand exchange in a defined cleavage on the strands and resolving on the strands S. Matsumoto L. Landy A. Cell. 1987; 50: 779-788Abstract Full Text PDF PubMed Scopus (185) Google Scholar, 10Kitts P.A. Nash H.A. Nucleic Acids Res. 1988; 16: 6839-6856Crossref PubMed Scopus (47) Google P.A. Nash H.A. Nature. 1987; 329: 346-348Crossref PubMed Scopus (127) Google Scholar, 18Kitts P.A. Nash H.A. J. Mol. Biol. 1988; 204: 95-107Crossref PubMed Scopus (73) Google Scholar). in the loxP site, the base pairs immediately 5′ to the cleavage sites in the λ-integrase sites are is a to the cleavage site and an A to the cleavage and Landy Landy A. EMBO J. 16: PubMed Scopus Google Scholar) found that the base pairs at these the resolution bias, to for the base pairs at the in the Flp target site are and Flp to a in the directionality of resolution P.D. J. Mol. Biol. PubMed Scopus Google Scholar). the directionality of resolution may be by other the order of strand exchange in the XerC/XerD recombination is by a mechanism two recombinases and additional accessory proteins (6Colloms S.D. McCulloch R. Grant K. Neilson L. Sherratt D.J. EMBO J. 1996; 15: 1172-1181Crossref PubMed Scopus (114) Google Scholar, M. Blakely G. Sherratt D.J. EMBO J. PubMed Scopus Google Scholar, B. Arciszewska L.K. Sherratt D.J. Mol. Cell. Full Text Full Text PDF PubMed Scopus (65) Google Scholar). The structures of Cre to a lox site show that Lys86 the of guanine at Lys86 is to contact the of at in the wild-type loxP site Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). is that Cre the bases at and via asymmetric contact with We found that of Lys86 to the resolution bias. the wild-type protein the resolution A the Cre mutant protein the for the immediately 5′ to the scissile Cre a for resolving to a that this bias may be to the DNA. the the of Cre to an A from a or a at and Lys86 is important for establishing the resolution for the strands with an A 5′ to the cleavage site a or a T. Lys86 may also have in resolution in to the two cleavage sites since the also the of resolution. were the resolution bias was abolished either by the or by identical base pairs at and that other factors such as the overlap sequence and the DNA of the χ or other amino acid may also influence the direction of resolution. the resolution bias of wild-type Cre and Cre may be by the asymmetric sequence at by the at and and and and to the of the asymmetric DNA by et Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar) in the of the Cre-lox and is that the sequences at these may DNA The Cre-lox structures other Lys86 that with the central 8-bp region of the and these asymmetric may also influence the order of strand exchange Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). we have that the asymmetric loxP sequence is important in the direction of resolution of Holliday structures by The bias in resolution be to the asymmetric Lys86 and the bases immediately 5′ to the cleavage sites. factors such as DNA DNA and other may also influence the direction of resolution of Holliday We and for

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.