ライフサイエンスコーパス: RNase H

1 RNase H active antisense oligonucleotides (ASOs) or smal

2 RNase H can act in a polymerization-dependent or polymer

3 RNase H can carry out primary and secondary cleavages du

4 RNase H can even effectively replace oligo(dT)-based met

5 RNase H cleavage and U1 protection assays suggest that p

6 RNase H cleavage and zinc coordination by NC were requir

7 RNase H enzymes facilitate the organisms to survive in t

8 RNase H enzymes sense the presence of ribonucleotides in

9 RNase H reduction was compounded by intrinsic RNase H de

10 c acids were designed as inhibitors of HIV-1 RNase H function.

11 Inhibition of HIV-1 RNase H is specific, as DNA synthesis is not affected.

12 er selective inhibitors also inhibited HIV-1 RNase H with low micromolar potencies.

13 For HIV-1 RNase H, the inclusion of the cognate dNTP enhanced DNA

14 ur findings provide insights into how type 2 RNase H activity is directed during genome replication a

15 in the polymerase region of RT, and the 428, RNase H Primer Grip Adjacent, and 507 sites, located in

16 epidum and demonstrated that it is an active RNase H and adopts the RNase H fold.

17 Additional RNase H cuts in the donor RNA allowed propagation to a m

18 -6, and -7 for M-MuLV significantly affected RNase H cleavage efficiency, while positions -7 and -12

19 P resistance without significantly affecting RNase H activity, whereas mutation in p51 caused NVP res

20 ucleic acids (LNAs) improve target affinity, RNase H activation and stability.

21 In general, the activity against RNase H was negligible, with only a few compounds active

22 Although RNase H mapping does not improve secondary structure pre

23 ique clade of RecA-like ATPase domain and an RNase H-like nuclease domain tethered by a regulatory li

24 n with an HIV-1-derived vector containing an RNase H-deficient reverse transcriptase (RT).

25 he domain responsible is reported to have an RNase H-like fold.

26 These results suggest that pUL15 uses an RNase H-like, metal ion-mediated catalysis mechanism for

27 Using an RNase H negative mutant RT, we showed that a polymer tra

28 igger mRNA degradation in the nucleus via an RNase H-dependent mechanism.

29 n analysis of R-loops in vivo, we develop an RNase-H-based approach; this reveals predominant R-loop

30 proteins--beta-lactamase, interleukin-2, and RNase H--even in the absence of any ligand.

31 ) possesses both DNA polymerase activity and RNase H activity that act in concert to convert single-s

32 ed the elevated strand transfer activity and RNase H activity, in addition to the loss of azidothymid

33 tations in the connection subdomain (CN) and RNase H domain of HIV-1 reverse transcriptase (RT) were

34 show that mixing the RT polymerase, CN, and RNase H domains from different subtypes can underestimat

35 e shown that mutations in the connection and RNase H domains of HIV-1 RT may also contribute to resis

36 Sequencing of the connection and RNase H domains of the HIV-2 patients did not reveal any

37 we analyzed the polymerase, connection, and RNase H domains of RT in HIV-2 patients failing NRTI-con

38 ulation, multiple RNA biogenesis factors and RNase H act as guardians of the genome.

39 eling studies based on both the HIV-1 IN and RNase H catalytic core domains provided new structural i

40 ment of these compounds as dual HIV-1 IN and RNase H inhibitors.

41 Single nucleotide incorporation and RNase H cleavage were examined using presteady-state kin

42 Microarray mapping and RNase H cleavage identified accessible sites for oligonu

43 g short, randomized DNA oligonucleotides and RNase H cleavage.

44 requires coordination of both polymerase and RNase H activities.

45 The p66 subunit contains the polymerase and RNase H catalytic sites.

46 evaluate movement of the DNA polymerase and RNase H domains.

47 RT content decreased both polymerization and RNase H activity in virions.

48 cting the balance between polymerization and RNase H activity.

49 t slow PPi release allows polymerization and RNase H to occur at comparable rates.

50 , thereby attaining what has eluded RNAi and RNase H experiments: elimination of MRP RNA in the major

51 oncoding RNAs that are resistant to RNAi and RNase H-based degradation.

52 report the synthesis, thermal stability, and RNase H substrate activity of 2'-deoxy-2',4'-difluoroara

53 e to the thumb and connection subdomains and RNase H domain of the p66 subunit as well as the thumb a

54 ported that the absence of Topoisomerase and RNase H activity in Escherichia coli or Saccharomyces ce

55 , reverse transcriptase (with its associated RNase H activity), and integrase.

56 ibited reverse transcriptase (RT) associated RNase H, implying potential dual target inhibition.

57 es, consistently inhibited HIV RT-associated RNase H and polymerase with IC50s in low to submicromola

58 ues consistently inhibited HIV RT-associated RNase H in the low micromolar range in the absence of si

59 man and HIV reverse transcriptase-associated RNase H-mediated cleavage of the complement RNA strand c

60 y common substrate between the two bacterial RNase H enzymes.

61 n to access the evolutionary history between RNases H from mesophilic and thermophilic bacteria.

62 In vivo, MTOs synthesized in both RNase H-activating and steric-blocking oligonucleotide d

63 uld serve to develop dual inhibitors of both RNase H and integrase.

64 s RT pausing and RNA template degradation by RNase H activity of the RT, subsequently leading to stra

65 oth PRI1 protein and ATP and is inhibited by RNase H treatment of the product of PRI1 synthesis.

66 e nucleotide modifications than tolerated by RNase H or RISC-dependent ASOs, with the goal of improvi

67 isense oligonucleotides (ASOs) that catalyze RNase H-mediated degradation of huntingtin mRNA, we demo

68 Overexpression of a cellular RNase H, which degrades RNA in an RNA:DNA hybrid, comple

69 ovirus and siphovirus orthologs and cellular RNase H, delineating a new evolutionary lineage among a

70 One of the two cellular RNases H may assist in this process.

71 Escherichia coli RNase H is known to populate an intermediate before the

72 The folding pathway of Escherichia coli RNase H is one of the best experimentally characterized

73 oMLV) RT and also inhibited Escherichia coli RNase H.

74 not inhibit the activity of Escherichia coli RNase H.

75 are removed by two evolutionarily conserved RNase H enzymes.

76 -drug RT but higher polymerization-dependent RNase H activity.

77 It should now be possible to design RNases H that display the desired thermophilic or mesoph

78 ect initial rates of the polymerase-directed RNase H activity but only polymerase-independent cleavag

79 ivo it ensures that RNase H2 is the dominant RNase H activity during nuclear replication.

80 Depleting endogenous RNase H activity impairs R-loop removal in Saccharomyces

81 d on these results, we propose that enhanced RNase H cleavage near the primer terminus plays a role i

82 s, a hydrolytic activity of the same enzyme (RNase H) is required to remove genomic RNA of the RNA/DN

83 ues have been tested on recombinant enzymes (RNase H and integrase) and in cell-based assays.

84 s target all HIV enzymatic activities except RNase H, which has proven to be a very difficult target

85 pendent exonuclease III, lambda exonuclease, RNase H, RNase HII, AP endonuclease, duplex-specific nuc

86 Finally, RNase H-based fragmentation analysis and 3-sequence anal

87 cleic acid conformation that is required for RNase H cleavage.

88 Mycobacterium smegmatis encodes four RNase H enzymes: RnhA, RnhB, RnhC and RnhD.

89 The addition of constraints from RNase H cleavage improves the prediction to 100% of base

90 The enzyme preserves the general 'RNase H-like motif' structure.

91 The enzyme exhibited greater RNase H activity in the presence of Mn2+ compared with M

92 raction with residues in the ribonuclease H (RNase H) active site and thumb subdomain of the p66 RT s

93 uplex in the vicinity of the ribonuclease H (RNase H) active site.

94 ed to allosterically inhibit ribonuclease H (RNase H) activity of human immunodeficiency virus type 1

95 rse transcriptase-associated ribonuclease H (RNase H) are both selective targets for HIV-1 chemothera

96 ng protein (MBP) and E. coli ribonuclease H (RNase H) as our model proteins, we monitored their unfol

97 Ribonuclease H (RNase H) belongs to the nucleotidyl-transferase superfam

98 Ribonuclease H (RNase H) cleavages and nucleocapsid protein (NC) were re

99 s polymerization-independent ribonuclease H (RNase H) cleavages of the donor template necessary for s

100 he interface between the p66 ribonuclease H (RNase H) domain and p51 thumb of human immunodeficiency

101 or the Q509L mutation in the ribonuclease H (RNase H) domain of HIV-1 reverse transcriptase (RT), whi

102 of ancestral proteins of the ribonuclease H (RNase H) family using ancestral sequence reconstruction

103 ranscriptase (RT) associated ribonuclease H (RNase H) for human immunodeficiency virus (HIV) drug dis

104 e well-characterized protein ribonuclease H (RNase H) from Escherichia coli populates an on-pathway i

105 ch the reverse transcriptase ribonuclease H (RNase H) has created a nick or short gap in the donor te

106 ranscriptase (RT) associated ribonuclease H (RNase H) remains an unvalidated antiviral target.

107 ranscriptase (RT)-associated ribonuclease H (RNase H) remains the only virally encoded enzymatic func

108 ranscriptase (RT) associated ribonuclease H (RNase H) remains the only virally encoded enzymatic func

109 vectors of Escherichia coli ribonuclease H (RNase H) were determined by NMR spin relaxation and comp

110 o displayed activity against ribonuclease H (RNase H).

111 olymerase, and RT-associated ribonuclease H (RNase H).

112 Ribonucleases H (RNases H) are endonucleases which cleave the RNA moiety

113 evious studies of bacterial ribonucleases H (RNases H) from the thermophile Thermus thermophilus and

114 In particular, ribonuclease HI (RNase H), an 18 kD globular protein that hydrolyzes the

115 delta), in Escherichia coli ribonuclease HI (RNase H).

116 chemotypes have been reported to inhibit HIV RNase H biochemically, few show significant antiviral ac

117 Although a number of inhibitors of HIV RNase H activity have been reported, few inhibit by dire

118 en the case for allosteric inhibition of HIV RNase H activity, providing a platform for designing imp

119 ble chemical scaffold for development of HIV RNase H inhibitors.

120 favorable binding to the active site of HIV RNase H, providing a basis for the design of more potent

121 of these analogues to the active site of HIV RNase H.

122 ajor challenge of specifically targeting HIV RNase H arises from the general lack of selectivity over

123 ossible challenges may be that targeting HIV RNase H is confronted with a steep substrate barrier.

124 simulations are reported for five homologous RNase H proteins of varying thermostabilities and enzyma

125 se activity and DNA-directed RNA hydrolysis (RNase H activity).

126 We have previously identified RNase H to be an HIV-1 protein that has the potential to

127 -activity relationship (SAR) for identifying RNase H inhibitors with antiviral activity.

128 on in p51 caused NVP resistance and impaired RNase H, demonstrating that NVP resistance may occur ind

129 C5 position that led to drastically improved RNase H inhibition and significant antiviral activity.

130 ation of the inhibitor and HIV-1 RT improves RNase H active site inhibitors and may circumvent the ob

131 explaining why R-tracts do not accumulate in RNase H-deficient cells, while double-strand breaks do.

132 ed to study the metal-ligand coordination in RNase H at different concentration of Mg(2+).

133 In conclusion, severe defects in RNase H activity alone, exemplified by the P236L mutant,

134 ance may occur independently from defects in RNase H function.

135 Moreover, in RNase H, the glutamate residue E188 has been shown to be

136 observed that the effect of the reduction in RNase H cleavage on NNRTI resistance is dependent upon t

137 y stall, so the failure of R-loop removal in RNase H-deficient bacteria becomes lethal.

138 nalysis shows that the catalytic residues in RNase H are preorganized on ps-ns time scales via a netw

139 ge assays, we show that degradation of RT in RNase H N-terminal mutants occurs in the absence of acti

140 is not required for the degradation of RT in RNase H N-terminal mutants, suggesting a role for a cell

141 e residues differs drastically from those in RNase H-like nucleases, suggesting a drifting of the act

142 the possibility of developing dual HIV-1 IN/RNase H inhibitors and obtaining new information for the

143 motherapy, and the identification of dual IN/RNase H inhibitors is an attractive strategy for new dru

144 The catalytically inactive RNase H mutation E478Q abolished this difference.

145 Indeed, RNase H-deficient cells have increased chromosomal rearr

146 ion-dependent and polymerization-independent RNase H were found to be important in creating efficient

147 pendent, but not polymerization-independent, RNase H.

148 ing modified nucleic acid residues to induce RNase H-mediated degradation of CUG-repeat transcripts.

149 ith an N-1 methyl group (9 and 10) inhibited RNase H in low micromolar range without significantly in

150 s the N-1 unsubstituted subtype 11 inhibited RNase H in submicromolar range and RT polymerase in low

151 type that potently and selectively inhibited RNase H without inhibiting HIV in cell culture.

152 primer (T/P), and consequently also inhibits RNase H activity.

153 Nase H reduction was compounded by intrinsic RNase H defects in the mutant RTs.

154 ient reverse transcriptase, (ii) introducing RNase H to break up the DNA:RNA hybrid, and (iii) adding

155 8495 bound to the active site of an isolated RNase H domain of HIV-1 RT at a resolution limit of 1.71

156 The isolated RNase H domain of M-MuLV reverse transcriptase retained

157 tion and a crystal structure of the isolated RNase H domain reveals that this compound can also bind

158 s with the C-terminal domain of eRF1 via its RNase H domain to sterically occlude the binding of pept

159 endonuclease activity is inhibited by known RNase H inhibitors.

160 MMLV RT enzymes lacking RNase H activity were shown to be more sensitive to RT-q

161 wimpy testis (PIWI) domain, which folds like RNase H and is responsible for target RNA cleavage in RN

162 ications within the oligonucleotide to limit RNase H cleavage of the non-targeted transcript.

163 ty to DNA antisense oligonucleotide-mediated RNase H digestion.

164 f protein folding and unfolding; both modern RNases H evolved to be more kinetically stable than thei

165 Promotion of read-through by MoMLV RNase H prevents nonsense-mediated mRNA decay (NMD) of m

166 nary DRIPc-seq experiments identified mostly RNase H-resistant but exosome-sensitive RNAs that mapped

167 to the division of labor among mycobacterial RNases H by deleting the rnhA, rnhB, rnhC and rnhD genes

168 This new RNase H folds through a pathway similar to that of the p

169 K103N and Y181C mutants had normal RNase H activity; V106A, G190A, and G190S mutants had mo

170 eans for structurally guided design of novel RNase H inhibitors.

171 cular, we found that the first amino acid of RNase H never varied in over 1,850 isolates of HIV-1 tha

172 e motion is achieved through the addition of RNase H, which selectively hydrolyses the hybridized RNA

173 CPV resolvase is dimer of RNase H superfamily domains related to Escherichia coli

174 ereby influences the catalytic efficiency of RNase H.

175 Similar results from a fragment of RNase H demonstrate that only half of the protein is sig

176 et out to trap the transient intermediate of RNase H at equilibrium by selectively destabilizing the

177 RP3-dependent responses, and introduction of RNase H, which degrades such hybrids, into infected cell

178 vels were altered by in vivo manipulation of RNase H levels did not form detectable R-loops, suggesti

179 scriptional efficiency, or overexpression of RNase H or C(1-3)A RNA can severely impair the type II t

180 le kinetic behavior can limit the potency of RNase H active site inhibitors.

181 ranscription is performed in the presence of RNase H, which specifically digests the RNA strands with

182 ance of the N-terminal amino acid residue of RNase H in the early life cycle of HIV-1.

183 that dictate the potency and selectivity of RNase H inhibition as well as the observed antiviral act

184 hich was inferred from structural studies of RNase H.

185 dinium chloride (GdmCl)-induced unfolding of RNase H also begins with the formation of the DMG.

186 Our data suggest that both versions of RNase H fold through a similar trajectory with similar h

187 ficant differences between the disruption of RNase Hs and Top1 in regards to the orientation-specific

188 Based on RNase H enzymology, we enhanced single nucleotide discri

189 Zinc supported optimal RNase H activity at approximately 25 muM, similar to the

190 pocket, but it does not perturb the optimal RNase H active conformation.

191 In the absence of Top1 or RNase Hs, R-loops accumulated to substantially higher ex

192 tions by chelating divalent metal at the p66 RNase H active site.

193 Proximity of the p51 thumb to the p66 RNase H domain implied that inhibitor binding altered ac

194 chemical hurdle in the development of potent RNase H inhibitors.

195 polymerization is efficient and processive, RNase H is inefficient and periodic.

196 rnhA mutant, which is incapable of producing RNase H and thus harbors increased levels of RNA:DNA hyb

197 e were interested in one particular protein, RNase H, that is cleaved from reverse transcriptase.

198 t formation of a complex with the prototypic RNase H inhibitor beta-thujaplicinol is slow, and, once

199 ition by Prp17, Cef1 and the reoriented Prp8 RNase H-like domain.

200 ote exon ligation, bind together to the Prp8 RNase H-like domain.

201 We identified a putative RNase H from Chlorobium. tepidum and demonstrated that i

202 rted to enhance NRTI resistance, also reduce RNase H cleavage and enhance NNRTI resistance in the con

203 we hypothesized that these mutations reduce RNase H cleavage and provide more time for the NNRTI to

204 549N, Q475A, and Y501A mutants, which reduce RNase H cleavage, enhance resistance to nevirapine (NVP)

205 n on both RNA and DNA templates, and reduced RNase H cleavage.

206 erences at a cleavage site direct retroviral RNase H specificity.

207 site influence the three types of retroviral RNase H activity: internal, DNA 3'-end-directed, and RNA

208 monstrate that all three modes of retroviral RNase H cleavage share sequence determinants that may be

209 The sequence preferences of retroviral RNase H likely reflect structural features in the substr

210 assays to identify inhibitors of retroviral RNases H.

211 Ribonuclease (RNase) H enzymes that recognize and process such embedde

212 s that efficiently inhibit the ribonuclease (RNase) H activity of the human immunodeficiency virus ty

213 The ribonuclease (RNase) H class of enzymes degrades the RNA component of

214 und F3284-8495 as a specific inhibitor of RT RNase H, with low micromolar potency in vitro.

215 substrate, the C-terminal helix E of the RT RNase H domain is dynamic, characterized by severe excha

216 ypes carefully designed to achieve selective RNase H inhibition.

217 tary elements that rely on the PPT sequence: RNase H sequence preference and incompatibility of the p

218 s over other single-stranded nucleases since RNase H is functional in physiological conditions.

219 s indicates that, in contrast to active site RNase H inhibitors, these thienopyrimidinones destabiliz

220 The loops are very stable and some RNase H resistant TERRA remains at the t-loop, likely ad

221 the folding trajectories of the three-state RNase H and the two-state RNase H, proteins with the sam

222 of the three-state RNase H and the two-state RNase H, proteins with the same native-state topology bu

223 ay similar to that of the previously studied RNases H.

224 During minus-strand DNA synthesis, RNase H degrades viral RNA sequences, generating potenti

225 tive against HIV-1 replication and targeting RNase H in vitro.

226 tructure in the unfolded state of C. tepidum RNase H is more restricted than that of T. thermophilus.

227 ilus RNase H, the folding core of C. tepidum RNase H plays an important role in the unfolded state of

228 with the p51 subunit lacking the C-terminal RNase H domain.

229 esembling those of bacteriophage terminases, RNase H, integrases, DNA polymerases, and topoisomerases

230 MD calculations support the hypothesis that RNase H can accommodate three divalent metal ions in its

231 Therefore, we propose that RNase H-deficient mutants convert some R-loops into R-tr

232 The RNase H active site of RT functions as a nuclease to cle

233 The RNase H activities of recombinant and virion-associated

234 The RNase H activity of reverse transcriptase carries out th

235 The RNase H activity of reverse transcriptase is required du

236 The RNase H structural fold defines a large family of nuclei

237 that it is an active RNase H and adopts the RNase H fold.

238 7u, and 8g were the most active against the RNase H activity of reverse-transcriptase, with IC50 val

239 RNA or a DNA template and did not alter the RNase H cleavage pattern.

240 Although the RNase H-dependent mechanism of inhibition of gene expres

241 cer, the reverse transcriptase (RT), and the RNase H domains.

242 rienting the RNA strand for catalysis at the RNase H active site.

243 reveals that this compound can also bind the RNase H site and retains the metal-dependent binding mod

244 position following a GA dinucleotide by the RNase H of reverse transcriptase (RT).

245 e relative titer of the virus and caused the RNase H of RSV RT to lose the ability to cleave the PPT

246 ported, few inhibit by directly engaging the RNase H active site.

247 I have closely examined the RNase H domain of Prp8 in each of the structures.

248 coordinate to two divalent metal ions in the RNase H active site.

249 of chelating two divalent metal ions in the RNase H active site.

250 ns in vif but instead a V27I mutation in the RNase H coding sequence.

251 cted by the ordering of D549 and H539 in the RNase H domain.

252 In the RNase H from Thermus thermophilus, the low DeltaC degree

253 Grip Adjacent, and 507 sites, located in the RNase H region.

254 Interestingly, the RNase H domain has different and unexpected roles in eac

255 p66 subunit and a p51 subunit that lacks the RNase H domain.

256 mical correlates of fitness by measuring the RNase H and polymerization activities of recombinant mut

257 rs closely mimic natural substrates near the RNase H domain, while their binding within the polymeras

258 pounds inhibited the polymerase, but not the RNase H function of Moloney Murine Leukemia Virus (MoMLV

259 the entire TP and RT domains and most of the RNase H domain were required for protein priming.

260 tic metals differs from other members of the RNase H family.

261 a previously uncharacterized version of the RNase H fold with multiple distinctive Zn-chelating moti

262 against IN and a moderate inhibition of the RNase H function of RT, confirming the possibility of de

263 The dynamic nature of the RNase H intermediate may be important for its role as an

264 results also indicate the importance of the RNase H N-terminal residue in the dimerization of RT sub

265 domain (amino acids 1-400, consisting of the RNase H, S1, 5'-sensor, and DNase I subdomains) of E. co

266 it is most similar to the RuvC family of the RNase H-like endonucleases.

267 Terminase nucleases resemble the RNase H-superfamily nucleotidyltransferases in folds, an

268 hese thermophilic proteins, we subjected the RNase H from Chlorobium tepidum to similar studies.

269 icinal chemistry data also revealed that the RNase H biochemical inhibition largely correlated the an

270 Additionally, we report that the RNase H complexes formed with one or both divalent ions

271 H/D exchange indicated that the RNase H domain of p66 is very flexible.

272 We found that the RNase H method performed best for chemically fragmented,

273 he bound nucleic acid prevents access to the RNase H active site, which represents a possible biochem

274 r RT, and the RNA strand moves closer to the RNase H active site.

275 yridinone-containing inhibitors bound to the RNase H active site.

276 g inhibitor and two Mn(II) ions bound to the RNase H active site.

277 extra structural elements in addition to the RNase H-like fold core and variations in local architect

278 ce degradation of complementary RNAs via the RNase H pathway and much is understood about that proces

279 RNA/DNA and increased interactions with the RNase H domain, including the interaction of a 2'-OH wit

280 ribed as well as its binding mode within the RNase H catalytic site to rationalize its selectivity.

281 sons with similar studies on T. thermophilus RNase H, identify new residues involved in this residual

282 c proteins reveals that like T. thermophilus RNase H, the folding core of C. tepidum RNase H plays an

283 ASOs that function through RNase H or the RNA-induced silencing complex (RISC) resu

284 the polypurine tract (PPT), is resistant to RNase H-mediated hydrolysis and subsequently serves as a

285 o a sequence that was otherwise resistant to RNase H.

286 ytic domain that is topologically similar to RNase H.

287 of genuine R-loops that responded in vivo to RNase H levels and displayed classical features associat

288 protein and additional reverse transcriptase-RNase H cleavage.

289 critical for fine tuning catalytic turnover, RNase H processing, and drug resistance.

290 AB mutant Escherichia coli, deficient in two RNase H enzymes that remove both R-loops and incorporate

291 the riboswitch regulatory mechanism, we used RNase H cleavage assays to probe the structure of nascen

292 ranscript is cleaved within the intron using RNase H, both the 5' and 3' cleavage fragments are detec

293 an inhibitor of human immunodeficiency virus RNase H, inhibited pUL89 endonuclease activity at low-mi

294 s (D67N, K70R, T215Y, and K219Q) on in vitro RNase H activity and AZT monophosphate (AZTMP) excision.

295 se stability, activity in vitro and in vivo, RNase H activation and cleavage patterns (both human and

296 The mobility changes were RNase H-resistant and therefore, unlikely to have been c

297 ng treatment of the transcribed plasmid with RNase H, which removes mRNA hybridized with the template

298 Pre-treatment with RNase H only partially suppressed instability, supportin

299 Subsequent treatment with RNase H releases RNA-templated ligation products into so

300 e system that allows strand transfer without RNase H activity.