A polymerase III-like reinitiation mechanism is operating in regulation of histone expression in archaea.
An archaeal histone gene from the hyperthermophile Pyrococcus furiosus containing four consecutive putative oligo-dT terminator sequences was used as a model system to investigate termination signals and the mechanism of termination in vitro. The archaeal RNA polymerase terminated with high efficiency at the first terminator at 90 degrees C when it contained five to six T residues, at 80 degrees C readthrough was significantly increased. A putative hairpin structure upstream of the first terminator had no effect on termination efficiency. Template competition experiments starting with RNA polymerase molecules engaged in ternary complexes revealed recycling of RNA polymerase from the terminator to the promoter of the same template. This facilitated reinitiation was dependent upon the presence of a terminator sequence suggesting that pausing at the terminator is required for recycling as in the RNA polymerase III system. Replacement of the sequences immediately downstream of the oligo-dT terminator by an AT-rich segment improved termination efficiency. Both AT-rich and GC-rich downstream sequences seemed to impair the facilitated reinitiation pathway. Our data suggest that recycling is dependent on a subtle interplay of pausing of RNA polymerase at the terminator and RNA polymerase translocation beyond the oligo-dT termination signal that is dramatically affected by downstream sequences.
Spitalny
Patrizia
P
Department of Microbiology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
Thomm
Michael
M
D001105:Archaea / Q000201:enzymology* / Q000378:metabolism; D019843:Archaeal Proteins / Q000378:metabolism*; D001483:Base Sequence; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D019848:Gene Expression Regulation, Archaeal; D006657:Histones / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic; D020027:Pyrococcus furiosus / Q000235:genetics*; D012320:RNA Polymerase III / Q000378:metabolism; D019642:RNA, Archaeal / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D013696:Temperature; D013728:Terminator Regions, Genetic; D024363:Transcription Initiation Site; D014158:Transcription, Genetic
D019843:Archaeal Proteins; D006657:Histones; D019642:RNA, Archaeal; D012321:DNA-Directed RNA Polymerases; D012320:RNA Polymerase III