Removal of a terminator structure by RNA processing regulates int gene expression.

The int gene of phage lambda encodes a protein involved in site-specific recombination. Its expression is regulated differentially during successive phases of the lambda infective cycle. The gene is transcribed early after infection from one promoter, pL, and later from a second promoter pI. Each transcription event requires different positive activation factors, lambda N and cII proteins, respectively. Transcription from the pI promoter, located adjacent to int, passes through int and terminates 277 nucleotides beyond int at tI. Polymerases initiating at pL transcribe through tI and into the b segment of lambda DNA. The read-through pL transcript is sensitive to cleavage by the endonuclease, RNase III, both in vivo and in vitro. Two specific cuts are made by RNase III in a double-stranded structure about 260 nucleotides beyond int in the location of the tI terminator. Functionally, the processed pL transcript is unable to synthesize the int gene product, whereas the terminated and unprocessed pI transcript expresses int. Interestingly, unprocessed pL transcripts made in hosts defective in RNase III (rnc-) can express int. Thus a correlation exists between processing and negative control of int expression. The place where processing occurs, some 260 nucleotides beyond int, is called sib, and the control of int expression from this site is called retroregulation. Retroregulation by sib is not restricted just to the int gene; we show that if the sib site is cloned beyond a bacterial gene, the gene is controlled by sib and RNase III. Specific models are discussed with respect to control of gene expression by RNase III from a site beyond the controlled gene.

[1]  Richard A. Young,et al.  The ribonuclease III site flanking 23S sequences in the 30S ribosomal precursor RNA of E. coli , 1980, Cell.

[2]  C. Richardson,et al.  Processing of mRNA by ribonuclease III regulates expression of gene 1.2 of bacteriophage T7 , 1981, Cell.

[3]  F. Studier,et al.  Effect of RNAase III, cleavage on translation of bacteriophage T7 messenger RNAs. , 1975, Journal of molecular biology.

[4]  S. R. Kushner,et al.  Amplification of ribonuclease II (rnb) activity in Escherichia coli K-12. , 1983, Nucleic acids research.

[5]  W. Szybalski,et al.  Transcription termination sites in the major leftward operon of coliphage lambda. , 1978, Virology.

[6]  W. Gilbert,et al.  Sequencing end-labeled DNA with base-specific chemical cleavages. , 1980, Methods in enzymology.

[7]  L. Enquist,et al.  Downstream regulation of int gene expression by the b2 region in phage lambda. , 1981, Gene.

[8]  D. Court,et al.  Deletion analysis of the retroregulatory site for the λint gene , 1983 .

[9]  H. Echols,et al.  Positive regulation of integrative recombination by the cII and cIII genes of bacteriophage λ , 1977 .

[10]  D. Court,et al.  Retroregulation: Control of gene expression from sites distal to the gene , 1982, Cell.

[11]  M. Belfort.  The cII-independent expression of the phage λ int gene in RNase III-defective E. coli , 1980 .

[12]  M. Belfort,et al.  Activation of the lambda int gene by the cii and ciii gene products. , 1976, Virology.

[13]  W. Ross,et al.  The λ phage att site: functional limits and interaction with Int protein , 1980, Nature.

[14]  W. Ross,et al.  Viral integration and excision: structure of the lambda att sites. , 1977, Science.

[15]  R. Kelley,et al.  DNA sequence of the att region of coliphage 434. , 1981, Gene.

[16]  D. Apirion,et al.  Antitermination and absence of processing of the leftward transcript of coliphage lambda in the RNAase III-deficient host. , 1977, Journal of molecular biology.

[17]  D. Court,et al.  Positively activated transcription of λ integrase gene initiates with UTP in vivo , 1981, Nature.

[18]  D. Apirion,et al.  The synthesis of some proteins is affected in RNA processing mutants of Escherichia coli. , 1980, Biochemical and biophysical research communications.

[19]  G. Guarneros,et al.  The regulation of integrative recombination by the b2 region and the cII gene of bacteriophage lambda. , 1979, Virology.