RNA Polymerase Marching Backward

Kassavetis, George A.; Ep, Geiduschek

doi:10.1126/science.7679800

Cited by 72 publications

(50 citation statements)

References 25 publications

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“…These findings are interesting in light of recent studies showing that RNA polymerases can cleave their transcripts nucleolytically (for review, see Kassavetis and Geiduschek 1993) and are also known to abort synthesis of transcripts shorter than 10 residues (for review, see von Hippel et al 1984). Thus, the ribonucleoprotein enzyme telomerase may share common properties with DNA-dependent RNA polymerases and may catalyze several substratespecific activities in vivo.…”

mentioning

confidence: 84%

“…Only 3 bp of interaction between product and template may be maintained during elongation. karyotic, and vaccinia virus DNA-dependent RNA polymerases (for review, see Kassavetis and Geiduschek 1993). The RNA polymerases catalyze a 3' ~ 5' nucleolytic product cleavage that is distinct from pyrophosphorolysis, the resynthesis of nucleotide triphosphates from pyrophosphate and the 3' residue of a polynucleotide (Kassavetis et al 1986).…”

Section: The Cleavage Activity Catalyzed By Telomerase Resembles Thatmentioning

confidence: 99%

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Tetrahymena telomerase catalyzes nucleolytic cleavage and nonprocessive elongation.

Collins¹,

Greider²

1993

Genes & Development

157

168

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Telomerase is a ribonucleoprotein enzyme that adds telomeric repeats to chromosomes, maintaining telomere length and stabilizing chromosome ends. In vitro, telomerase from the ciliate Tetrahymena elongates single-stranded, guanosine-rich DNA primers by adding repeats of the Tetrahymena telomeric sequence, dT2G4. We have identified two activities of Tetrahymena telomerase in addition to the previously described processive elongation reaction: a 3'-5' nucleolytic cleavage of primer or product DNA and a nonprocessive mode of elongation. The nucleolytic cleavage activity removed residues not conforming to the telomeric repeat sequence from a primer 3' end, eliminating mismatch between DNA primer and RNA template sequences. Template-matched residues were also cleaved from primer or product DNA. Specific primer lengths, sequences, and concentrations stimulated cleavage and processive or nonprocessive elongation differentially. These newly identified activities suggest that telomerase may catalyze a range of telomere synthesis and repair functions and suggest mechanistic similarities between telomerase and RNA polymerase enzymes. On the basis of our results, we propose a model for telomerase primer binding, cleavage, and elongation.

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mentioning

confidence: 84%

Section: The Cleavage Activity Catalyzed By Telomerase Resembles Thatmentioning

confidence: 99%

Tetrahymena telomerase catalyzes nucleolytic cleavage and nonprocessive elongation.

Collins¹,

Greider²

1993

Genes & Development

157

168

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“…Recent studies from several laboratories indicate that chain elongation by all RNA polymerases involves a series of fonward movements interspersed with pauses (see the review by Kassavetis and Geiduschek (1993) for references to this field). At a pause site at least three different outcomes are possible: (i) the polymerase can stay paused forever and never go further fonward (stall); (ii) it can release from the template (terminate); or, (iii) it can eventually proceed on through the pause site.…”

Section: Relating Poii Termination To Transcript Eiongation Mechanismmentioning

confidence: 99%

“…When polll encounters an intrinsic pause site, elongation factor SII induces cleavage of the transcript leading to a 5' fragment and a 3' fragment. The 3 fragment is released while the 5' fragment is re-elongated through the pause site (reviewed by Kassavetis and Geiduschek, 1993). B.…”

Section: Acknowiedgementsmentioning

confidence: 99%

The mechanism of transcription termination by RNA poiymerase I

Reeder

Lang

1994

Molecular Microbiology

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SummaryEukaryotic ribosomal gene transcription units are bordered at their 3 ends by short DNA sequences which specify site-specific termination by RNA polymerase i (poii). Poll terminators from yeast through to mammals appear to follow similar rules: they contain a site for a sequence-specific DNA-binding protein; they function only in one orientation; 3 ends are formed upstream of the binding site; and 5 fianking sequences influence the position and efficiency of 3 end formation. Recent progress in understanding the mechanism of RNA chain elongation by other polymerases suggests a model for poll termination in which termination is seen as one of the severai outcomes possible when a polymerase encounters a pause site.

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“…GreA and GreB of E. coli enhance the intrinsic cleavage by E. coli RNAP (25,27,28). GreA and GreB (and a eucaryotic counterpart, SII) prevent elongation arrest (29). GreA may participate in the fidelity of RNA synthesis (30).…”

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confidence: 99%

Nuclease Activity of T7 RNA Polymerase and the Heterogeneity of Transcription Elongation Complexes

Sastry

Ross

1997

Journal of Biological Chemistry

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We have discovered that T7 RNA polymerase, purified to apparent homogeneity from overexpressing Escherichia coli cells, possesses a DNase and an RNase activity. Mutations in the active center of T7 RNA polymerase abolished or greatly decreased the nuclease activity. This nuclease activity is specific for single-stranded DNA and RNA oligonucleotides and does not manifest on double-stranded DNAs. Under the conditions of promoter-driven transcription on double-stranded DNA, no nuclease activity was observed. The nuclease attacks DNA oligonucleotides in mono-or dinucleotide steps. The nuclease is a 3 to 5 exonuclease leaving a 3 -OH end, and it degrades DNA oligonucleotides to a minimum size of 3 to 5 nucleotides. It is completely dependent on Mg 2؉ . The T7 RNA polymerase-nuclease is inhibited by T7 lysozyme and heparin, although not completely. In the presence of rNTPs, the nuclease activity is suppressed but an unusual 3 -end-initiated polymerase activity is unmasked. RNA from isolated preelongation and elongation complexes arrested by a psoralen roadblock or naturally paused at the 3 -end of an oligonucleotide template exhibited evidence of nuclease activity. The nuclease activity of T7 RNA polymerase is unrelated to pyrophosphorolysis. We propose that the nuclease of T7 RNA polymerase acts only in arrested or paused elongation complexes, and that in combination with the unusual 3 -end polymerizing activity, causes heterogeneity in elongation complexes. Additionally, during normal transcription elongation, the kinetic balance between nuclease and polymerase is shifted in favor of polymerase.Transcription by procaryotic DNA-dependent RNA polymerases can be represented as follows (Scheme I).Elongation Termination SCHEME I. Representation of a transcription cycle. Open complexes synthesize short RNAs (up to 10 nts) during abortive initiation. After clearing the promoter, RNAP enters the elongation phase. Termination occurs at certain DNA sequences in either a factor-dependent or a factor-independent manner (2). The current view of transcription elongation has been possible because of our ability to arrest elongation at specific sites on DNA templates, partial purification of arrested complexes, and the enzymatic and chemical probing of their structures (3-17).The unexpected discovery of an RNA cleavage reaction in arrested Escherichia coli complexes (18) was followed by documentation of analogous cleavage reactions in other RNAPs (19 -23). E. coli RNAP and eucaryotic RNAP II are capable of RNA cleavage in binary and ternary complexes (24 -26). GreA and GreB of E. coli enhance the intrinsic cleavage by E. coli RNAP (25,27,28). GreA and GreB (and a eucaryotic counterpart, SII) prevent elongation arrest (29). GreA may participate in the fidelity of RNA synthesis (30).T7 RNAP (98.8 kDa) belongs to a class of single-subunit RNAPs that includes T3 and SP6 phage RNAPs (31-33). The three-dimensional structure of T7 RNAP shows high ␣-helicity with a deep cleft. Using a novel photochemical cross-linking technique, we have id...

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RNA Polymerase Marching Backward

Cited by 72 publications

References 25 publications

Tetrahymena telomerase catalyzes nucleolytic cleavage and nonprocessive elongation.

Tetrahymena telomerase catalyzes nucleolytic cleavage and nonprocessive elongation.

The mechanism of transcription termination by RNA poiymerase I

Nuclease Activity of T7 RNA Polymerase and the Heterogeneity of Transcription Elongation Complexes

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