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The Bacteroides fragilis Pathogenicity Island Is Contained in a Putative Novel Conjugative Transposon. Augusto A. Franco, 2004.The genetic element flanking the Bacteroides fragilis pathogenicity island [BfPAI] in enterotoxigenic B . fragilis [ETBF] strain 86-5443-2-2 and a related genetic element in NCTC 9343 were characterized . The results suggested that these genetic elementsare members of a new family of conjugative transposons [CTns]not described previously . These putative CTns, designated CTn86and CTn9343 for ETBF 86-5443-2-2 and NCTC 9343, respectively,differ from previously described Bacteroides species CTns ina number of ways . These new transposons do not carry tetQ, andthe excision from the chromosome to form a circular intermediateis not regulated by tetracycline; they are predicted to differin their mechanism of transposition; and their sequences havevery limited similarity with CTnDOT or other described CTns.CTn9343 is 64,229 bp in length, contains 61 potential open readingframes, and both ends contain IS21 transposases . Colony blothybridization, PCR, and sequence analysis indicated that CTn86has the same structure as CTn9343 except that CTn86 lacks a  7-kb
region containing truncated integrase [int2] and rteA genes
and it contains the BfPAI integrated between the mob region
and the bfmC gene . If these putative CTns were to be demonstrated
to be transmissible, this would suggest that the bft gene can
be transferred from ETBF to nontoxigenic B . fragilis strains
by a mechanism similar to that for the spread of antibiotic
resistance genes.
Transcription by Methanothermobacter thermautotrophicus RNA Polymerase In Vitro Releases Archaeal Transcription Factor B but Not TATA-Box Binding Protein from the Template DNA. Yunwei Xie, 2004.Transcription initiation in Archaea requires the assembly ofa preinitiation complex containing the TATA- box binding protein[TBP], transcription factor B [TFB], and RNA polymerase [RNAP].The results reported establish the fate of Methanothermobacter thermautotrophicus TBP and TFB following transcription initiation by M . thermautotrophicus RNAP in vitro . TFB is released after initiation, during extension of the transcript from 4 to 24 nucleotides, but TBP remains bound to the template DNA . Regulationof archaeal transcription initiation by a repressor competitionwith TBP for TATA-box region binding must accommodate this observation.
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