DNA-dependent poly (G) synthesizing activities in DNA-dependent RNA polymerase fractions from cauliflower inflorescence

Terminal uridylyl transferase of Vigna unguiculata: purification and characterization of an enzyme catalyzing the addition of a single UMP residue to the 3'-end of an RNA primer

An enzyme which catalyzes the addition of a single UMP residue from UTP to the 3'-end of an RNA primer and which is referred to as terminal uridylyl transferase (TUT) has been extensively purified from the membrane fraction of vigna unguiculata leaves. The purification procedure involved (i) solubilization by cation depletion (ii) DEAE-Sepharose CL-6B column chromatography (iii) affinity chromatography of poly(U)-Sepharose 4B and (iv) glycerol gradient centrifugation. The molecular weight of the native enzyme was approximately 50,000 as determined by velocity sedimentation. Under conditions that were optimal for UMP-incorporation (5 mM Mg2+, low salt, 30 degrees C) TUT displayed a marked specificity for UTP as substrate, was unable to incorporate deoxyribonucleoside triphosphates and required a single-stranded oligo- or polyribonucleotide as primer. When oligoA20, tRNAasp of E. coli or alfalfa mosaic virus RNA 4 were used as primers at various substrate to primer ratio's, the vast majority of the product appeared to consist of primer molecules elongated with a single UMP residue as shown by polyacrylamide gelelectrophoresis and nearest neighbour analysis. We believe TUT to be a novel enzyme which has not been reported before and which may be a feasible tool in RNA sequencing as it enables the specific 3'-terminal labeling of RNA molecules.

Conversion of Escherichia coli RNA polymerase to a template independent enzyme

Preparations of RNA polymerase (E.C.2.7.7.6) from uninfected Escherichia coli, T4 infected Escherichia coli, and Acinetobacter calcoaceticus when centrifuged in sucrose gradients in the absence of magnesium ions gave rise to five peaks, all of which were able to form polymers from ribonucleoside 5'-triphosphates in the absence of template or primer. All of the peaks obtained from the Escherichia coli enzyme appeared to contain the subunit alpha and beta and, in addition, polypeptides which appeared to be derived from the subunit beta.

Poly(A)-containing RNA from Petroselinum hortense: isolation, properties and messenger function in vitro

Cell suspension cultures from parsley (Petroselinum hortense Hoffm.) were labelled in vivo with [2-3H] adenosine. The RNA isolated from the ribosomal pellet was fractionated on an oligo(dT)-cellulose column. Approximately 1.5% of the RNA, representing about 15% of the total radioactivity, was retained at high salt concentrations and eluted at low ionic strength. As determined by two independent methods, this fraction contained poly(A) segments with an average length of about 80 nucleotides. It was active as template in a cell-free system from wheat germ, directing the synthesis of peptides ranging in molecular weight from about 4000-40000 daltons.