Author/Editor		Braun, Veit; Mehlig, Markus; Moos, Michael; Rupnik, Maja; Kalt, Bettina; Mahony, David E; von Eichel-Streiber, Christoph
Title		A chimeric ribozyme in Clostridium difficile combines features of group I introns and insertion elements
Type		članek
Source		Mol Microbiol
Vol. and No.		Letnik 36, št. 6
Publication year		2000
Volume		str. 1447-59
Language		eng
Abstract		Cd/St1, a DNA insertion of 1975 bp, was identified within tcdA-C34, the enterotoxin gene of the Clostridium difficile isolate C 34. Located in the catalytic domain A1-C34, Cd/St1 combines features of two genetic elements. Within the first 434 nt structures characterstic for group I introns were found; encoding the two transposase-like proteins tlpA and tlpB nucleotides 435-1975 represent the remainder of a IS605-like insertion element. We show that the entire Cd/St1 is accurately spliced from tcdA-C34 primary transcripts and that purified Tcdč-C34 toxin is of regulat size and catalytic activity. A search for Cd/St1-related sequences demonstrates that the element is widespread in toxinogenic and non-toxinogenic C. difficile strains, indicating the mobility of Cd/St1. In strain C34, we characterize 10 Cd/St1 variants; all are highly homologous to Cd/St1 (>93% identity), integrated in bacterial open reading frames (ORFs), show the typical composite structure of Cd/St1 and are precisely spliced from their primary transcripts. Cd/St1-like chimeric ribozymes appear to combine the invasiveness of an insertion element with the splicing ability of a group I intron, rendering transposition harmless for the interrupted gene.
Descriptors		CLOSTRIDIUM DIFFICILE INTRONS DNA INSERTION ELEMENTS ENTEROTOXINS POLYMERASE CHAIN REACTION SEQUENCE ANALYSIS, RNA