Antitermination increases the transcription of genes that are located downstream of terminators. Phage HK022 antiterminates transcription of its early genes by converting host RNA polymerase to a terminator- resistant form. This requires cis-acting phage sequences called nut sites. The isolation and characterization of nut region mutants argue that the sites are about 70 bases long and act as RNA transcripts consisting of two adjacent stem-loops. These transcripts presumably interact with a recognition site on RNA polymerase. The properties of polymerase mutants that are unable to antiterminate HK022 early transcription but are normal in all other respects tested suggest that the recognition site is located in a zinc-binding domain of the beta' subunit. The modified polymerase is capable of reading through at least three successive strong transcription terminators with much increased efficiency. The efficiency is greater than 90% per terminator in vivo and about 50% in vitro, consistent with the hypothesis that the requirements for persistent antitermination in the HK022 system are extraordinarily simple. The integrase proteins of phages lambda and HK022 are closely related site-specific recombinases that recognize different nucleotide sequences in the core regions of their substrates, the attachment sites of the two phages. The two proteins differ by 92 amino acid substitutions. We have found that no more than 5 of these substitutions are critical for the different DNA sequence specificities of these enzymes. Two of these substitutions act principally by reducing specificity, while the other three act principally by specifically decreasing activity on one of the substrates.

Project Start
Project End
Budget Start
Budget End
Support Year
25
Fiscal Year
1995
Total Cost
Indirect Cost
City
State
Country
United States
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Sloan, Sieghild; Rutkai, Edit; King, Rodney A et al. (2007) Protection of antiterminator RNA by the transcript elongation complex. Mol Microbiol 63:1197-208
Rutkai, Edit; Gyorgy, Andrea; Dorgai, Laszlo et al. (2006) Role of secondary attachment sites in changing the specificity of site-specific recombination. J Bacteriol 188:3409-11
King, Rodney A; Markov, Dmitry; Sen, Ranjan et al. (2004) A conserved zinc binding domain in the largest subunit of DNA-dependent RNA polymerase modulates intrinsic transcription termination and antitermination but does not stabilize the elongation complex. J Mol Biol 342:1143-54
Gottesman, Max E; Weisberg, Robert A (2004) Little lambda, who made thee? Microbiol Mol Biol Rev 68:796-813
King, Rodney A; Sen, Ranjan; Weisberg, Robert A (2003) Using a lac repressor roadblock to analyze the E. coli transcription elongation complex. Methods Enzymol 371:207-18
King, Rodney A; Weisberg, Robert A (2003) Suppression of factor-dependent transcription termination by antiterminator RNA. J Bacteriol 185:7085-91
Weisberg, Robert A; Storz, Gisela (2002) Take your vitamins with a pinch of RNA. Mol Cell 10:1266-8
Sen, Ranjan; King, Rodney A; Mzhavia, Nino et al. (2002) Sequence-specific interaction of nascent antiterminator RNA with the zinc-finger motif of Escherichia coli RNA polymerase. Mol Microbiol 46:215-22
Sen, R; King, R A; Weisberg, R A (2001) Modification of the properties of elongating RNA polymerase by persistent association with nascent antiterminator RNA. Mol Cell 7:993-1001
King, R A; Madsen, P L; Weisberg, R A (2000) Constitutive expression of a transcription termination factor by a repressed prophage: promoters for transcribing the phage HK022 nun gene. J Bacteriol 182:456-62