The ligation and flexibility of four-arm DNA junctions.
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Base Composition↗
Biomedical subjects
M L Petrillo
Publications and source records attributed to M L Petrillo.
Three-arm nucleic acid junctions are flexible.
Nucleic acid junctions are stable analogs of branched DNA structures which occur transiently in living systems. We show here that junctions which contain three double helical arms can be enzymatically oligomerized, using conventional sticky-ended ligation procedures, to create larger complexes. The products consist of a series of linked junctions separated by 20 base pairs. Junction dimers are formed that have free termini only, whereas trimers and larger species are found to be both unclosed and cyclized. The formation of a series of macrocyclic products which, surprisingly, begins with trimers and tetramers indicates that this junction is flexible about a bending axis, and perhaps twist-wise as well. We have obtained the same results from three different 3-arm junctions, two in which the junction is flanked by a 3 Watson-Crick base pairs, and one in which a G-G base pair flanks the junction.
Base Composition↗
A self-splicing RNA excises an intron lariat.
We have investigated the in vitro self-splicing of a class II mitochondrial intron. A model pre-mRNA containing intron 5 gamma of the oxi 3 gene of yeast mitochondrial DNA undergoes an efficient intramolecular rearrangement reaction in vitro. This reaction proceeds under conditions distinct from those optimal for self-splicing of class I introns, such as the Tetrahymena nuclear rRNA intron. Intron 5 gamma is excised as a nonlinear RNA indistinguishable from the in vivo excised intron product by gel electrophoresis and primer extension analysis. Studies of the in vitro excised intron product strongly indicate that it is a branched RNA with a circular component joined by a linkage other than a 3'-5' phosphodiester. Two other products, the spliced exons and the broken form of the lariat, were also characterized. These results show that the class II intron products are similar to those of nuclear pre-mRNA splicing.
DNA, Mitochondrial↗