Selectivity and proofreading both contribute significantly to the fidelity of RNA polymerase III transcription.
We examine here the mechanisms ensuring the fidelity of RNA synthesis by RNA polymerase III (Pol III). Misincorporation could only be observed by using variants of Pol III deficient in the intrinsic RNA cleavage activity. Determination of relative rates of the reactions producing correct and erroneous transcripts at a specific position on a tRNA gene, combined with computational methods, demonstrated that Pol III has a highly efficient proofreading activity increasing its transcriptional fidelity by a factor of 10(3) over the error rate determined solely by selectivity (1.8 x 10(-4)). We show that Pol III slows down synthesis past a misincorporation to achieve efficient proofreading. We discuss our findings in the context of transcriptional fidelity studies performed on RNA Pols, proposing that the fidelity of transcription is more crucial for Pol III than Pol II.
Alic
Nazif
N
Commissariat à l'Energie Atomique, Institut de Biologie et de Technologies de Saclay, F-91191 Gif sur Yvette Cedex, France.
Ayoub
Nayla
N
Landrieux
Emilie
E
Favry
Emmanuel
E
Baudouin-Cornu
Peggy
P
Riva
Michel
M
Carles
Christophe
C
D001483:Base Sequence; D019295:Computational Biology; D014644:Genetic Variation; D007700:Kinetics; D008954:Models, Biological; D021122:Protein Subunits / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D012313:RNA / Q000096:biosynthesis*; D012320:RNA Polymerase III / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012343:RNA, Transfer / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D013698:Templates, Genetic; D014157:Transcription Factors / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism; D014158:Transcription, Genetic
D021122:Protein Subunits; D011994:Recombinant Proteins; D014157:Transcription Factors; D012313:RNA; D012343:RNA, Transfer; D012320:RNA Polymerase III