ライフサイエンスコーパス: Pol III

1 Pol III acts on lifespan downstream of TORC1, and limiti

2 Pol III inhibition affects gene reactivation status alon

3 Pol III regulation is thus sensitive to environmental cu

4 Pol III subunits Rpc53 and Rpc37 (C53/37) form a heterod

5 Pol III transcription at tRNA genes (tDNAs) requires the

6 Pol III was found to bind near many known genes as well

7 Pol III-dependent transcription was independent of the i

8 o determine the intranuclear positions of 13 Pol III-transcribed genes.

9 orresponding to the Rpc82/34/31 and Rpc53/37 Pol III-specific subcomplexes.

10 Conversely, ectopic insertion of a Pol III-transcribed gene in the vicinity of a centromere

11 DNA polymerase III holoenzyme depends upon a Pol III-tau-psi-chi-SSB binding network, where SSB is bo

12 opriate access to the replication fork via a Pol III*-Pol IV switch relying on both the rim and cleft

13 Accordingly, Pol III activity is tightly regulated with cell growth a

14 To reach maximum activity, Pol III binds to the DNA sliding clamp beta and the exon

15 A 2000-fold purification of Pol III* (all Pol III HE subunits except beta) from this strain contai

16 units are common to Pol I (a.k.a. Pol A) and Pol III (a.k.a. Pol C) and are encoded by single genes.

17 factors (GRFs) Reb1p, Rap1p, and Abf1p, and Pol III transcription factors enhance the efficiency of

18 ed that alcohol increases TBP expression and Pol III gene transcription to promote liver tumor format

19 ment of CE to Pol II as opposed to Pol I and Pol III rests on the interaction between CE and the phos

20 new nomenclature system for plant Pol I and Pol III subunits in which the 12 subunits that are struc

21 me that the major DNA polymerases (Pol I and Pol III) and DNA ligase are directly involved with oligo

22 ymerases I and III (abbreviated as Pol I and Pol III), the first analysis of their physical compositi

23 ted to parts of these factors (for Pol I and Pol III).

24 which are normally transcribed by Pol I and Pol III.

25 eraction with Pol II as opposed to Pol I and Pol III.

26 with the functional divergence of Pol I- and Pol III-specific AC40 paralogs.

27 on factor, which regulates Pol I, Pol II and Pol III gene activity.

28 functional conservation of human Pol II and Pol III pre-initiation complexes.

29 ted mechanism of exchange between Pol II and Pol III that occurs outside the replication fork.

30 target negative regulators of RNA Pol II and Pol III to coordinately increase the transcription of ho

31 or a close similarity between the Pol II and Pol III transcription complexes, and additionally explai

32 s reveal that the interactions of Pol II and Pol III with beta allow for rapid exchange during DNA sy

33 olymerases, abbreviated as Pol I, Pol II and Pol III.

34 ed transcription to a mixture of Pol II- and Pol III-, or to a solely Pol III-dependent initiation of

35 s reveal a novel mechanism by which MAF1 and Pol III regulate the activity of a protein-coding gene t

36 transcription by interfering with TFIIIB and Pol III.

37 ntially, the drugs did not affect Pol-II and Pol-III transcription, demonstrating a high selectivity.

38 e circadian clock, which allows anticipatory Pol III transcription.

39 lear accumulation, binding to RNA Pol III at Pol III genes and transcriptional repression.

40 All but the INR also reside at Pol III promoters, where TBP makes similar contacts.

41 Autonomous Pol III transcription was also revealed for Alus nested

42 span; in flies, longevity can be achieved by Pol III inhibition specifically in intestinal stem cells

43 clamp adjacent to the cleft that is bound by Pol III* before gaining control of the same cleft that i

44 g control of the same cleft that is bound by Pol III*.

45 insertions upstream of genes transcribed by Pol III indicated that Ty1 preferentially integrates int

46 Outside of genes transcribed by Pol III, Ty1 avoids coding sequences, a pattern that is

47 ism by which TORC1 controls transcription by Pol III.

48 II (Pol III) transcription enhances cellular Pol III gene production, leading to an increase in trans

49 ination by isolated Saccharomyces cerevisiae Pol III.

50 stream of the primer terminus and chaperones Pol III into that position, preventing competition by SS

51 e that loads beta(2) onto DNA and chaperones Pol III onto the newly loaded beta(2).

52 of collision release by the Escherichia coli Pol III polymerase.

53 promoter being directly responsive to a core Pol III transcription factor complex.

54 sceptibility to challenge by exogenous D403E Pol III*.

55 Only when D403E Pol III was bound to a tau-containing DnaX complex did e

56 lar interactions occurring at Brf2-dependent Pol III promoters and highlighting the general structura

57 same beta clamp and to positively dissociate Pol III from beta clamp in a concentration-dependent man

58 enzymatic activities of the replicative DNA Pol III are well understood, its dynamics within the rep

59 tion and stress conditions by Maf1 to enable Pol III regulation.

60 er, and germline mutations in genes encoding Pol III subunits or tRNA processing factors cause neurog

61 esis under normal conditions but facilitates Pol III displacement from the primer terminus following

62 t RNA secondary structure, which facilitates Pol III release.

63 ith dNTPs at the active site of the C-family Pol III replicase at a step that does not require correc

64 t corroborate their findings using bona fide Pol III from two laboratory sources.

65 herefore identify a radical new function for Pol III in the regulation of macrophage function which m

66 einitiation complex but are not required for Pol III recruitment.

67 -IN but not two other complexes required for Pol III transcription, transcription initiation factors

68 reminiscent of the minimal requirements for Pol III to replicate short single-stranded DNA-binding p

69 y recovered via two sequential switches from Pol III to Pol IV and back to Pol III.

70 Furthermore, Pol-III inhibition abrogates IFN-beta induction by the i

71 ranscription of RNA Pol III-dependent genes (Pol III genes), tRNA(Leu), tRNA(Tyr), 5S rRNA and 7SL RN

72 Here we report global Pol III expression/methylation profiles and molecular me

73 k into account tRNA redundancies by grouping Pol III occupancy into 46 anticodon isoacceptor families

74 lamp), in the presence of primase, helicase, Pol III core, clamp loader, and beta-clamp initiates DNA

75 Hence, Pol III is a pivotal mediator of this key nutrient-signa

76 Whereas higher Pol III occupancy during the night reflects a MAF1-depen

77 only required to serve as a scaffold to hold Pol III and chi in the same complex.

78 hether or not DNA polymerase III holoenzyme (Pol III HE) contains gamma.

79 al replicase, DNA polymerase III holoenzyme (Pol III HE).

80 Understanding how Pol III-dependent microRNAs subvert cellular and viral p

81 Initiation of human Pol III from TATA box-containing Pol II promoters under

82 oinformatic pipeline allowing us to identify Pol III-dependent transcripts of individual Alu elements

83 an antimutator allele of DNA polymerase III (Pol III) alpha-subunit (dnaE915) and either chromosomal

84 ation that involves both RNA polymerase III (Pol III) elements and CCCTC binding factor (CTCF) sites.

85 BocaSR is transcribed by RNA polymerase III (Pol III) from an intragenic promoter at levels similar t

86 equired for Escherichia coli polymerase III (Pol III) holoenzyme association at the replication origi

87 coded tau subunit of the DNA polymerase III (Pol III) holoenzyme.

88 RNA polymerase III (Pol III) is one of three eukaryotic transcription comple

89 DNA polymerase III (Pol III) is the catalytic alpha subunit of the bacterial

90 al. characterized their RNA polymerase III (Pol III) preparation and concluded that it requires an R

91 -152) was proficient for DNA polymerase III (Pol III) replication in vitro.

92 AF1 (CsMAF1) protein, an RNA polymerase III (Pol III) repressor that controls ribosome biogenesis and

93 RNA polymerase III (Pol III) synthesizes short noncoding RNAs, many of which

94 RNA polymerase III (Pol III) synthesizes tRNAs and other small noncoding RNA

95 RNA polymerase III (Pol III) transcribes medium-sized non-coding RNAs (colle

96 Deregulation of RNA polymerase III (Pol III) transcription enhances cellular Pol III gene pr

97 Deregulation of RNA polymerase III (Pol III) transcription enhances cellular tRNAs and 5S rR

98 ons bound in vivo by the RNA polymerase III (Pol III) transcription factor III C (TF(III)C) complex,

99 he 'master' repressor of RNA polymerase III (Pol III) transcription in yeast, and is conserved in euk

100 RNA polymerase III (Pol III) transcription of tRNA genes is essential for ge

101 ansposon Ty3 is found at RNA polymerase III (Pol III) transcription start sites of tDNAs.

102 f1, a known repressor of RNA polymerase III (Pol III) transcription.

103 They contain a polymerase, polymerase III (Pol III), a beta(2) processivity factor, and a DnaX comp

104 non-coding RNA genes by RNA polymerase III (Pol III), but the precise role of this ribonucleoprotein

105 hase of transcription by RNA polymerase III (Pol III), the enzyme that synthesizes the majority of RN

106 st, we demonstrated that RNA polymerase III (Pol III)-transcribed genes such as tRNA and 5S rRNA gene

107 The association of RNA polymerase III (Pol III)-transcribed genes with nucleoli seems to be an

108 e integrates upstream of RNA polymerase III (Pol III)-transcribed genes, yet the primary determinant

109 oduction of noncanonical RNA polymerase III (Pol III)-transcribed viral microRNAs in leukemic B cells

110 scripts that are made by RNA polymerase III (Pol III).

111 of genes transcribed by RNA polymerase III (Pol III).

112 ransposon transcribed by RNA polymerase III (Pol III).

113 ication of DNA-dependent RNA polymerase III (Pol-III) as the enzyme responsible for synthesizing 5'-p

114 We have approached this using immobilized Pol III-nucleic acid scaffolds to examine the two major

115 two potential C31 variants were detected in Pol III.

116 hypothesis have claimed that gamma found in Pol III HE might be a proteolysis product of tau.

117 We find that a reduction in Pol III extends chronological lifespan in yeast and orga

118 that, for the first time, alcohol increases Pol III gene transcription through a response element, w

119 have reported that alcohol intake increases Pol III gene transcription to promote cell transformatio

120 les of Pol III genes suggest that individual Pol III genes are exquisitely regulated by transcription

121 alysis has demonstrated that alcohol induces Pol III gene transcription.

122 FIIIB and that overexpression of p65 induces Pol III-dependent transcription.

123 Hyper-methylation of Pol III genes inhibits Pol III binding to DNA via inducing repressed chromatin

124 subunit and either protein can assemble into Pol III.

125 Pol I and the other of which assembles into Pol III.

126 Pol II was found to bind near many known Pol III genes, including tRNA, U6, HVG, hY, 7SK and prev

127 n lifespan downstream of TORC1, and limiting Pol III activity in the adult gut achieves the full long

128 By mapping Pol III occupancy genome-wide in mouse, rat, human, maca

129 tal anomalies, suggesting that BRF1-mediated Pol III transcription is required for normal cerebellar

130 Using an in vitro assay to monitor Pol III*-Pol IV switching, we determined that a single c

131 and c-Myc, also tightly associate with most Pol III-transcribed genes.

132 ctopic insertion of Pol III genes into a non-Pol III gene locus results in the centromeric localizati

133 ghly resistant to dilution in the absence of Pol III* in solution.

134 S28ph has a critical role in the activity of Pol III genes.

135 Inhibiting the activity of Pol III in the gut of adult worms or flies is sufficient

136 y; the growth-promoting anabolic activity of Pol III mediates the acceleration of ageing by TORC1.

137 s as a sensor that regulates the affinity of Pol III to the clamp in the presence of ssDNA.

138 ion of the active rRNA genes by Pol I and of Pol III-transcribed genes.

139 This centromeric association of Pol III genes, mediated by the condensin complex, become

140 al DNA arrays resulted in the association of Pol III-transcribed genes with nucleoli.

141 We conclude that the association of Pol III-transcribed genes with the nucleolus, when permi

142 s catalytic inactivation and backtracking of Pol III, thus committing the enzyme to termination and t

143 MAF1 knockdown indicated enhanced binding of Pol III and BRF1, as well as of CFP1, p300, and PCAF, wh

144 with concomitant reduction in the binding of Pol III and Brf1.

145 ionally integrated with the active center of Pol III during termination.

146 Chaperoning of Pol III by the DnaX complex provides a molecular explana

147 e formation of the initiation sub-complex of Pol III.

148 The evolutionary conservation of Pol III affirms its potential as a therapeutic target.

149 ical role in alcohol-induced deregulation of Pol III genes in liver tumor development.

150 ociated with alcohol-induced deregulation of Pol III genes.

151 class of mutant mapped to the PHP domain of Pol III alpha, ablating interaction with the proofreadin

152 Dysregulation of Pol III transcription has been linked to cancer, and ger

153 Examination of Pol III* with varying composition of tau or the alternat

154 A three-tau form of Pol III HE would contain three Pol IIIs.

155 sembly, indicating that the dominant form of Pol III* in cells is Pol III2tau2 gammadeltadelta'chipsi

156 Intriguingly, a significant fraction of Pol III transcription from non-coding regions is not sub

157 , of RNase P is critical for the function of Pol III in cells and in extracts.

158 emonstrate the role of BRCA1 in induction of Pol III genes by alcohol and uncover a novel mechanism o

159 of these effects, we show that inhibition of Pol III activity in macrophages restrains cytokine secre

160 rthermore, we find that ectopic insertion of Pol III genes into a non-Pol III gene locus results in t

161 representing a third species of this kind of Pol III-dependent viral noncoding RNA and the first nonc

162 evealed an overall decrease in the levels of Pol III-transcribed tRNAs and an imbalance in the levels

163 We show that the centromeric localization of Pol III genes is mediated by condensin, which interacts

164 related with the centromeric localization of Pol III genes.

165 yeast extracts revealed that the majority of Pol III subunits co-purify with Ty1-IN but not two other

166 Similarity between termination mechanisms of Pol III and bacterial RNA polymerase suggests that hairp

167 ylation profiles and molecular mechanisms of Pol III regulation that have not been as extensively stu

168 Hyper-methylation of Pol III genes inhibits Pol III binding to DNA via induci

169 on by mTOR and suggest that normalization of Pol III activity may contribute to the therapeutic effic

170 a-amanitin reduced expression of a number of Pol III genes (e.g., U6, hY, HVG), suggesting that Pol I

171 o coordinate transcription and processing of Pol III transcripts in C. elegans.

172 environmental cues, yet a diurnal profile of Pol III transcription activity is so far lacking.

173 A 2000-fold purification of Pol III* (all Pol III HE subunits except beta) from this

174 TFIIIB is required for recruitment of Pol III and to promote the transition from a closed to a

175 f the gene, but the nucleolar recruitment of Pol III-transcribed genes required active transcription.

176 tions were associated with the 5' regions of Pol III transcribed genes; alignment of Ty1 insertion si

177 light a new and unique mode of regulation of Pol III transcription by mTOR and suggest that normaliza

178 ear localization and the rapid repression of Pol III in the nucleus.

179 MAF1 is a repressor of Pol III transcription whose activity is controlled by ph

180 1-dependent response to feeding, the rise of Pol III occupancy before the onset of the night reflects

181 Emerging diverse roles of Pol III genes suggest that individual Pol III genes are

182 f protein-coding genes has left the roles of Pol III in organismal physiology relatively unexplored.

183 itself was also enriched at the same set of Pol III templates, but this association was not influenc

184 ncrease in the occupancy of Maf1 on a set of Pol III-dependent genes, with concomitant reduction in t

185 nucleosome-bound factor enriched at sites of Pol III transcription, determines preferred target sites

186 ture of chromatin characteristic of sites of Pol III transcription.

187 ere, we show that the extensive structure of Pol III-synthesized transcripts dictates the release of

188 etween Ty1 integrase and the AC40 subunit of Pol III and demonstrate that AC40 is the predominant det

189 The polymerase catalytic subunit of Pol III, alpha, contains a PHP domain that not only bind

190 ion affects alcohol-induced transcription of Pol III genes.

191 , PTEN and Maf1 repress the transcription of Pol III genes.

192 minant targeting Ty1 integration upstream of Pol III-transcribed genes.

193 ediate insertion of Ty1 elements upstream of Pol III-transcribed genes.

194 ng Ty1-IN to insert Ty1 elements upstream of Pol III-transcribed genes.

195 ut, unexpectedly, bound many oligoadenylated Pol III transcripts, predominately pre-tRNAs.

196 Given the opposite effects of RecA on Pol III and TLS replisomes, we propose that RecA acts as

197 does not affect the ability of repression on Pol III genes.

198 mote the transition from a closed to an open Pol III pre-initiation complex, a process dependent on t

199 crease is observed in mutants of TF(III)B or Pol III subunits, demonstrating a specific role for the

200 s and, most prominently, pre-tRNAs and other Pol III transcripts are targeted for oligoadenylation an

201 get regions upstream of tRNA genes and other Pol III-transcribed genes when retrotransposing to new s

202 To determine the extent to which other Pol III-transcribed genes serve as genomic targets for T

203 n contained one molecule of gamma-C(tag) per Pol III* assembly, indicating that the dominant form of

204 omplex of Pol II, the replicative polymerase Pol III core complex and the dimeric processivity clamp,

205 Using a dominant negative D403E polymerase (Pol) III alpha that can form initiation complexes and se

206 nd both the alpha subunit of DNA polymerase (Pol) III and chipsi.

207 replication is performed by DNA polymerase (Pol) III.

208 ultaneously bind the replicative polymerase (Pol) III and the conserved Y-family Pol IV, enabling exc

209 RNA polymerase (Pol) III is the essential, evolutionarily conserved enzy

210 ion of gene transcription by RNA polymerase (Pol) III requires the activity of TFIIIB, a complex form

211 Transcription termination by RNA polymerase (Pol) III serves multiple purposes; it delimits interfere

212 Brf2 recruits RNA polymerase (Pol) III to type III gene-external promoters, including

213 ration of precursor tRNAs by RNA polymerase (Pol) III transcription to end maturation and modificatio

214 As) and tRNAs transcribed by RNA polymerase (Pol) III.

215 e active in transcription by RNA polymerase (Pol) III.

216 A sensors (DAI, AIM2, DDx41, RNA polymerase [Pol] III, and IFI16 [p204]) have been identified in rece

217 Compared to the alternative polymerases, Pol III transcription dominates during mid-exponential p

218 -circle synthesis by the fully reconstituted Pol III replisome.

219 ping effect, which indicates that recruiting Pol III was required for activation of Pol II-mediated t

220 ription factor IIIB (TFIIIB), which recruits Pol III to target genes.

221 Moreover, BRF1 mutations reduce Pol III-related transcription activity in vitro.

222 rapamycin kinase complex 1 (TORC1) regulates Pol III activity, and is also an important determinant o

223 ng module capable of specifically regulating Pol III transcriptional output in living cells.

224 h both a stalled and an actively replicating Pol III* in a manner that was independent of the rim con

225 ely studied, using nc886 as a representative Pol III gene.

226 ch is a BRCA1 deficient cell line, represses Pol III gene transcription.

227 MAF1 represses Pol III-mediated transcription by interfering with TFIII

228 occurs upstream of genes transcribed by RNA Pol III, requires the Ty1 element-encoded integrase (IN)

229 omatin environment with marked peaks for RNA Pol III and a number of histone modifications, suggestin

230 1 is a specific transcription factor for RNA Pol III genes.

231 CsMAF1 bound the human RNA Pol III and rescued the yeast maf1 mutant by repressing

232 e determined whether H3ph is involved in RNA Pol III transcription.

233 The products of RNA Pol III (RNA polymerase III) dependent genes are elevate

234 significantly increased transcription of RNA Pol III-dependent genes (Pol III genes), tRNA(Leu), tRNA

235 inding studies with bacterially purified RNA Pol III proteins demonstrate that Rpc31, Rpc34, and Rpc5

236 Trap purification of multiple GFP-tagged RNA Pol III subunits from yeast extracts revealed that the m

237 lation, nuclear accumulation, binding to RNA Pol III at Pol III genes and transcriptional repression.

238 1-IN interacts in vivo and in vitro with RNA Pol III-specific subunits to mediate insertion of Ty1 el

239 Although an interplay of several Pol III subunits is known to collectively control these

240 Similarly, Pol III occupancy of amino acid isotypes is almost invar

241 ture of Pol II- and Pol III-, or to a solely Pol III-dependent initiation of transcription from Pol I

242 elics (iYGR033c and ZOD1), and six non-tDNA, Pol III-transcribed types of genes (RDN5, SNR6, SNR52, R

243 m-sized non-coding RNAs (collectively termed Pol III genes).

244 Depletion of Nrd1 or Nab3 stabilized tested Pol III transcripts and their oligoadenylation was depen

245 We present evidence that Pol III-transcribed genes such as tRNA and 5S rRNA genes

246 caque, dog and opossum livers, we found that Pol III binding to individual tRNA genes varies substant

247 add more direct evidence to the notion that Pol III elements are able to directly influence Pol II g

248 This raises the possibility that Pol III is involved in ageing.

249 Here, I report that Pol III can, like Pol II, initiate transcription from mo

250 We show that Pol III efficiently terminates transcription in the abse

251 Here we show that Pol III limits lifespan downstream of TORC1.

252 We then show that Pol III occupancy of its target genes rises before the o

253 These findings suggest that Pol III stalled at the transpososome is exploited for co

254 These results suggest that Pol III transcription is involved in chromatin structure

255 In addition, the Pol III mutation was found to exert complex downstream e

256 rmation of an initiation complex between the Pol III HE and primed DNA.

257 easing concentrations of Pol II displace the Pol III core during DNA synthesis in a minimal reconstit

258 essed chromatin and is a determinant for the Pol III repertoire.

259 ent evidence points to a larger role for the Pol III transcription system in various other nuclear pr

260 e results provide compelling support for the Pol III*-Pol IV two-step switch model and demonstrate im

261 n sharp contrast, RecA severely inhibits the Pol III replisome.

262 ions bound by TFIIIC without the rest of the Pol III complex, and bound TFIIIC alone is also able to

263 Here, we discuss potential roles of the Pol III gene-mediated genome organization during interph

264 hinery, and that transcription levels of the Pol III genes are negatively correlated with the centrom

265 omponents bind immediately downstream of the Pol III preinitiation complex but are not required for P

266 alled "extra-transcriptional effects" of the Pol III system are reviewed here, and a model is put for

267 ere, we characterize the architecture of the Pol III-clamp-exonuclease complex by chemical crosslinki

268 zing purified components to reconstitute the Pol III*-Pol II switch in vitro indicated that Pol II sw

269 und to the displaced strand, stabilizing the Pol III-template interaction.

270 Here, we test the accepted view that the Pol III holoenzyme remains stably associated within the

271 Previous work in vitro demonstrated that the Pol III transcription factor (TF) IIIB is important for

272 labeled polymerases to demonstrate that the Pol III* complex (holoenzyme lacking the beta2 sliding c

273 h fluorescence microscopy, we found that the Pol III* subassembly frequently disengages from the repl

274 how that Rrn7 is most closely related to the Pol III general factor Brf1.

275 vered that PR physically associated with the Pol III holoenzyme.

276 how that p65 can directly associate with the Pol III transcription factor TFIIIB and that overexpress

277 iated by condensin, which interacts with the Pol III transcription machinery, and that transcription

278 e-tau form of Pol III HE would contain three Pol IIIs.

279 Thus, Pol III expression during tumorigenesis is delineated by

280 Thus, Pol III transcription during the diurnal cycle is regula

281 switches from Pol III to Pol IV and back to Pol III.

282 enesis, the fraction of actively transcribed Pol III genes increases reaching a plateau during immort

283 ndensin onto RNA polymerase III-transcribed (Pol III) genes and highly transcribed Pol II genes; cond

284 teins and initiation factors of translation, Pol III and rDNA.

285 We found that two Pol III elements within the promoter region influence AN

286 that can effectively compete with wild-type Pol III alpha and form initiation complexes, but cannot

287 ically with tRNA and snoRNA genes undergoing Pol III transcription.

288 U6, HVG, hY, 7SK and previously unidentified Pol III target genes.

289 When Pol III genes are hypo-methylated, MYC amplifies their t

290 tly and accurately bypass this adduct, while Pol III replicase, Pol IV, and Pol V were strongly inhib

291 eading frames not previously associated with Pol III transcription, suggesting the existence of a sma

292 lex, but are not necessarily associated with Pol III transcription.

293 Pol IV has a unique ability to coexist with Pol III on the same beta clamp and to positively dissoci

294 tion and chromatin looping concurrently with Pol III recruitment.

295 sites in the yeast genome that interact with Pol III transcription complexes.

296 Simultaneous knockdown with Pol III abolished these regulatory events.

297 Simultaneous knockdown of MAF1 with Pol III or BRF1 (subunit of TFIIIB) diminished the activ

298 er, beta(+)/beta(C) interacted normally with Pol III, and stimulated replication to the same extent a

299 the mechanism used by Pol IV to switch with Pol III* is distinct from those used by the other Pols.

300 erences in how Pol IV and Pol II switch with Pol III*.