Disease relevance of lacI

• Cell killing and mutation induction by cis- and trans-Pt(NH3)2Cl2 in Escherichia coli were examined by studying forward mutagenesis in the lacI gene in cells with different repair capacities [1].
• Recovery of lacI- genes from F is based on the conversion of this lacI+Z- alpha phage to lacI-Z+ alpha by recombination with F'lacI-Z+ [2].
• The chromosomal DNA that lies between the lacI and lacZ genes of Klebsiella pneumoniae constitutes a 196-base pair intercistronic region that contains regulatory sequences for both genes [3].
• High-level, inducible expression of heterologous genes in the cyanobacterium Synechococcus sp. strain PCC 7942 was obtained using the Escherichia coli trc promoter and lacI repressor [4].
• We have investigated the use of various Epstein-Barr virus (EBV)-based vectors bearing the two components of the Escherichia coli lac operator-repressor (lacO, lacI) complex [5].

High impact information on lacI

• DNA recognition by lac repressor and catabolite activator protein is greatly stimulated, while specific aroH DNA recognition by trp repressor is inhibited [6].
• Thus lac repressor-operator complexes can form on primate chromosomes and stringently block transcription from an adjoining promoter [7].
• Monkey cell lines that constitutively synthesize 38.6 kd lac repressor protein and bear stably integrated chloramphenicol acetyl transferase (CAT) genes linked to a lac operator-containing SV40 early promoter-enhancer were generated [7].
• Stringent regulation of stably integrated chloramphenicol acetyl transferase genes by E. coli lac repressor in monkey cells [7].
• Repression of large T synthesis or CAT activity occurred in vivo only when the respective operator-containing plasmid was cotransfected with a plasmid encoding lac repressor, or when the recipient cells stably synthesized lac repressor [8].

Chemical compound and disease context of lacI

• In the absence of excision repair, doxorubicin caused a striking (41-fold) increase in the frequency of large deletion mutations extending from the lac operator (lacO) into the lac repressor gene (lacI) of Escherichia coli [9].
• We have isolated the in vivo messenger RNA encoding the lactose repressor protein of Escherichia coli by hybridization to lacI gene DNA, and have verified its identity by characterizing specific fragments derived from its 5' and 3' ends [10].
• Suppressible base substitution mutations induced by angelicin (isopsoralen) in the Escherichia coli lacI gene: implications for the mechanism of SOS mutagenesis [11].
• Effect of deficiency in excision repair and umuC function on the mutagenicity with ethylene oxide in the lacI gene of E. coli [12].
• Sites of preferential induction of cyclobutane pyrimidine dimers in the nontranscribed strand of lacI correspond with sites of UV-induced mutation in Escherichia coli [13].

Biological context of lacI

• Transcription of the Escherichia coli lac repressor gene (lacI) in vivo produces monocistronic mRNAs with discrete 3' ends in the lac control region, although the DNA sequence of this region does not specify a strong termination signal of the traditional form [14].
• Doxorubicin-induced single base substitutions were highly focused at one site (4 of 6) in the i-d region of lacI, in contrast to the spontaneous distribution of point mutations, where 16 mutants were recovered at 12 different sites [9].
• The sequencing of over 6000 lacI- mutations has revealed 193 missense mutations generating 189 amino acid replacements at 102 different sites within the lac repressor [15].
• There is also 25% identity between the amino acid sequence of lacI and the deduced amino acid sequence of ebgR [16].
• In addition to this effect on transversions within the lacI gene, one previously recognized A.T-->G.C base-pair substitution hotspot in the lac operator is also reduced (approximately 5-fold) [17].

Anatomical context of lacI

• We, therefore, investigated the activity of Lac repressor artificially attached to the Escherichia coli cytoplasmic membrane [18].
• In lacI protoplasts the presence of IPTG manifested itself in a 4.2-fold relief of repression [19].
• The bacterial gene lacI, carried on a shuttle vector, is introduced into human tissue culture cells by transfection and allowed to replicate in the cell nucleus [20].
• To investigate the mutagenic effect of advanced glycosylation in mammalian cells, plasmid DNA containing the lacI mutagenesis marker was modified by advanced glycosylation endproducts in vitro, transfected into murine lymphoid cells, recovered, and analyzed for mutations, plasmid size changes, and the presence of shared insertion sequences [21].
• This modified lacI gene should be valuable for improved adaptation of the prokaryotic regulatory system to eukaryotic cells [22].

Associations of lacI with chemical compounds

• The 5'-endpoints of doxorubicin-induced lacO and lacI/lacO deletions occurred at the DNA sequence 5'-pyTAA or 5'-AATpy (where py is pyrmidine) (16%), at runs of purines or pyrimidines (41%) and adjacent to 5'-dGdC or 5'-dCdG doublets (34%) [9].
• To broaden our knowledge about the mutagenic specificity of SOS-dependent mutagens, we determined the mutational specificity of 233 suppressible lacI mutations induced by angelicin [11].
• However, characterization of lacI nonsense mutations induced by thymine starvation demonstrated that G:C----A:T transitions and all four possible transversions also occurred [23].
• Subsequent introduction of the lacI gene into IIB1 cells resulted in correct transcriptional repression of the lacZ gene that could be alleviated by IPTG, an allosteric inducer of lacI repression [24].
• (3) There was no observable preference for particular sequences of furazolidone-induced mutations; the prominent hotspots for AF2-induced G:C-->T:A transversions, G:C-->A:T transitions and -(G:C) frameshifts were at 5'-TGC-3' sequences in the lacI gene [25].

Regulatory relationships of lacI

• The heavy chain and the light chain-gIII fusion are transcribed as a polycistronic mRNA from the lacZ promoter and efficient transcriptional control is provided by wildtype lacI present on the vector [26].

Other interactions of lacI

• Analysis of reverse mutations in lacZ and forward nonsense mutations in lacI showed that the mutA strain has higher levels of A.T----T.A and G.C----T.A transversions, and to a lesser degree A.T----C.G transversions [27].
• To investigate the specificity of these antimutator effects, we have analyzed spectra of forward mutations in the N-terminal part of the lacI gene (i-d mutations) for two of the mutL dnaE derivatives (dnaE911 and dnaE915), as well as the control mutL strain [28].
• Searches of the Y. pestis genome databases revealed the presence of noncontiguous sequences highly homologous to Escherichia coli lacZ, lacY, and lacI [29].
• Strain MM6-13 (ptsI suc lacI sup) of Escherichia coli contains a suppressor of the succinate-negative phenotype [30].
• The lac repressor from the lacI gene and the chimeric protein from a hupB' ::lac'Z fusion gene, whose start codons are GUG, were also synthesised in the deletion mutant [31].

Analytical, diagnostic and therapeutic context of lacI

• This system proved to be operational (1) to suppress UAG mutations by wobble pairing in an E. coli lacI-lacZ gene fusion and (2) to read through at least eight UAA glutamine codons in a Paramecium alpha-tubulin gene, as detected by Western blotting and colony hybridization [32].
• lac repressor: crystallization of intact tetramer and its complexes with inducer and operator DNA [33].
• Amino-acid sequence of lac repressor from Escherichia coli. Isolation, sequence analysis and sequence assembly of tryptic peptides and cyanogen-bromide fragments [34].
• We have determined the DNA alterations recovered after treatment with (+-)-r-7,t-8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+-)-anti-BPDE] in the lacI gene of excision-repair-deficient (Uvr-) Escherichia coli [35].
• In this study, a 302 bp segment of the Escherichia coli lacI gene was amplified and the product purified by liquid chromatography on a Mono Q column [36].

References