Biomaterial Database

Coupling of lac mRNA transcription to translation in Escherichia coli cell extracts. 1978

K A Jacobs, and V Shen, and D Schlessinger

In an extract containing all the components for lac gene expression except washed ribosomes, lac mRNA formation was increased 4- to 6-fold by the addition of washed ribosomes. The formation of beta-galactosidase mRNA and enzyme showed very different dependency on added ribosomes. Enzyme was formed in proportion to the number of ribosomes added, whereas 10% of the standard level of ribosomes promoted full levels of transcription. Consistent with their action in vivo, chloramphenicol and erythromycin blocked the ribosome-dependent lac transcription. The same inhibition was seen with RNA pulse-labeled for 1 or 5 min, so that the effect was truly a blockage of formation rather than an increased hyperlability of nascent mRNA. The effect was specified for some RNA species, as it is in vivo: phage lambda N gene transcription was increased rather than inhibited in the presence of chloramphenicol. Chloramphenicol did not stop lac transcription as a result of its blockage of formation of the regulatory nucleotide tetraphosphate (ppGpp), because addition of the nucleotide did not restore mRNA formation in chloramphenicol-treated extracts. Rather, the data are consistent with the ideas that one or a few ribosomes moving closely behind RNA polymerase can prevent its arrest and that, when ribosome movement is blocked by chloramphenicol, the RNA polymerase is exposed to factors that provoke premature RNA chain termination.

UI	MeSH Term	Description	Entries
D002474	Cell-Free System	A fractionated cell extract that maintains a biological function. A subcellular fraction isolated by ultracentrifugation or other separation techniques must first be isolated so that a process can be studied free from all of the complex side reactions that occur in a cell. The cell-free system is therefore widely used in cell biology. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p166)	Cellfree System,Cell Free System,Cell-Free Systems,Cellfree Systems,System, Cell-Free,System, Cellfree,Systems, Cell-Free,Systems, Cellfree
D002701	Chloramphenicol	An antibiotic first isolated from cultures of Streptomyces venequelae in 1947 but now produced synthetically. It has a relatively simple structure and was the first broad-spectrum antibiotic to be discovered. It acts by interfering with bacterial protein synthesis and is mainly bacteriostatic. (From Martindale, The Extra Pharmacopoeia, 29th ed, p106)	Cloranfenicol,Kloramfenikol,Levomycetin,Amphenicol,Amphenicols,Chlornitromycin,Chlorocid,Chloromycetin,Detreomycin,Ophthochlor,Syntomycin
D004926	Escherichia coli	A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.	Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D005696	Galactosidases	A family of galactoside hydrolases that hydrolyze compounds with an O-galactosyl linkage. EC 3.2.1.-.	Galactosidase
D006159	Guanosine Tetraphosphate	Guanosine 5'-diphosphate 2'(3')-diphosphate. A guanine nucleotide containing four phosphate groups. Two phosphate groups are esterified to the sugar moiety in the 5' position and the other two in the 2' or 3' position. This nucleotide serves as a messenger to turn off the synthesis of ribosomal RNA when amino acids are not available for protein synthesis. Synonym: magic spot I.	Alarmone ppGpp,Bacterial Magic Spot ppGpp,Guanosine 5'-(trihydrogen diphosphate), mono(trihydrogen diphosphate) (ester),Guanosine 5'-diphosphate 2'(3')-diphosphate,ppGpp,Guanosine 3'-Diphosphate 5'-Diphosphate,Guanosine 5'-Diphosphate 3'-Diphosphate,3'-Diphosphate 5'-Diphosphate, Guanosine,5'-Diphosphate 3'-Diphosphate, Guanosine,Guanosine 3' Diphosphate 5' Diphosphate,Guanosine 5' Diphosphate 3' Diphosphate,Tetraphosphate, Guanosine,ppGpp, Alarmone
D001616	beta-Galactosidase	A group of enzymes that catalyzes the hydrolysis of terminal, non-reducing beta-D-galactose residues in beta-galactosides. Deficiency of beta-Galactosidase A1 may cause GANGLIOSIDOSIS, GM1.	Lactases,Dairyaid,Lactaid,Lactogest,Lactrase,beta-D-Galactosidase,beta-Galactosidase A1,beta-Galactosidase A2,beta-Galactosidase A3,beta-Galactosidases,lac Z Protein,Protein, lac Z,beta D Galactosidase,beta Galactosidase,beta Galactosidase A1,beta Galactosidase A2,beta Galactosidase A3,beta Galactosidases
D012270	Ribosomes	Multicomponent ribonucleoprotein structures found in the CYTOPLASM of all cells, and in MITOCHONDRIA, and PLASTIDS. They function in PROTEIN BIOSYNTHESIS via GENETIC TRANSLATION.	Ribosome
D012321	DNA-Directed RNA Polymerases	Enzymes that catalyze DNA template-directed extension of the 3'-end of an RNA strand one nucleotide at a time. They can initiate a chain de novo. In eukaryotes, three forms of the enzyme have been distinguished on the basis of sensitivity to alpha-amanitin, and the type of RNA synthesized. (From Enzyme Nomenclature, 1992).	DNA-Dependent RNA Polymerases,RNA Polymerases,Transcriptases,DNA-Directed RNA Polymerase,RNA Polymerase,Transcriptase,DNA Dependent RNA Polymerases,DNA Directed RNA Polymerase,DNA Directed RNA Polymerases,Polymerase, DNA-Directed RNA,Polymerase, RNA,Polymerases, DNA-Dependent RNA,Polymerases, DNA-Directed RNA,Polymerases, RNA,RNA Polymerase, DNA-Directed,RNA Polymerases, DNA-Dependent,RNA Polymerases, DNA-Directed
D012333	RNA, Messenger	RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.	Messenger RNA,Messenger RNA, Polyadenylated,Poly(A) Tail,Poly(A)+ RNA,Poly(A)+ mRNA,RNA, Messenger, Polyadenylated,RNA, Polyadenylated,mRNA,mRNA, Non-Polyadenylated,mRNA, Polyadenylated,Non-Polyadenylated mRNA,Poly(A) RNA,Polyadenylated mRNA,Non Polyadenylated mRNA,Polyadenylated Messenger RNA,Polyadenylated RNA,RNA, Polyadenylated Messenger,mRNA, Non Polyadenylated
D014158	Transcription, Genetic	The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.	Genetic Transcription