The Ohio State University

The University of Texas System

Huatao Guo

Alan M Lambowitz

Steven Zimmerly

Georg Mohr

Jian Yang

Clifford James Beall

Michael Karberg

Allen M Lambowitz

Roland Saldanha

Manabu Matsuura

Jiam Yang

The present invention provides a system and methods for analyzing the function of nucleotide integrases and modified group II introns. The system comprises a donor plasmid comprising a wild-type or modified group II intron, a recipient plasmid comprising a DNA recognition site and a promoterless reporter gene downstream of the DNA target site, and a host cell. The method comprises the steps of transforming a host cell with the donor and recipient plasmids, assaying for expression of the reporter gene, isolating plasmid DNA from the cotransformed cells, and analyzing the plasmid DNA to confirm that the group II intron has been inserted into the target sequence. The present invention also provides a method for simultaneously analyzing the activity of two or more modified nucleotide integrases. The present invention also relates to methods of preparing a library of donor plasmids containing a plurality of diverse modified group II intron DNA sequences.

Methods for analyzing the insertion capabilities of modified group II introns

Methods, employing a nucleotide integrase, for cleaving single-stranded RNA substrates, single-stranded DNA substrates, and double-stranded DNA substrates at specific sites and for inserting a nucleic acid molecule into the cleaved substrate are provided. One method uses a nucleotide integrase to cleave one strand of a double-stranded DNA substrate. The method comprises the steps of: providing an isolated nucleotide integrase comprising a group II intron RNA having two hybridizing sequences for hybridizing with two intron RNA binding sequences on the top strand of the DNA substrate, and a group II-intron encoded protein which binds to a first sequence element of the substrate; and reacting the nucleotide integrase with the double-stranded DNA substrate to permit the nucleotide integrase to cleave the top strand of the DNA substrate and to insert the group II intron RNA into the cleavage site. The method of cleaving both strands of a double-stranded DNA substrate comprises the steps of: providing a nucleotide integrase comprising a group II intron RNA having two hybridizing sequences for hybridizing with two intron RNA binding sequences on one strand of the substrate, and a group II-intron encoded protein that interacts with a first sequence element and a second sequence element in the recognition site of the substrate; and reacting the nucleotide integrase with the double-stranded DNA substrate such that the nucleotide integrase cleaves both strands of the DNA substrate and inserts the group II intron RNA into the cleavage site of the one strand. The method for cleaving a single-stranded nucleic acid substrate comprises the steps of: providing a nucleotide integrase having two hybridizing sequences for hybridizing with two intron RNA-binding sequences on the single-stranded substrate, and a group II intron encoded protein; and reacting the nucleotide integrase with the single stranded nucleic acid substrate to allow the nucleotide integrase to cleave the substrate and to attach the group II intron RNA molecule thereto.

Methods for cleaving single-stranded and double-stranded DNA substrates with nucleotide integrase

Methods for preparing nucleotide integrases are provided. The nucleotide integrases are prepared by combining in vitro an excised, group II intron RNA, referred to hereinafter as 'exogenous RNA', with a group II intron-encoded protein. The exogenous RNA is prepared by in vitro transcription of a DNA molecule which comprises a group II intron sequence. In one embodiment, the group II intron-encoded protein is made by introducing into a host cell a DNA molecule that comprises at least the open reading frame sequence of a group II intron and then expressing the open reading frame sequence in the host cell. The DNA molecule may comprise the open reading frame sequence operably linked to a promoter, preferably an inducible promoter. Thereafter, the cell is fractionated and the protein is recovered and combined in vitro with the exogenous RNA to provide RNP particles having nucleotide integrase activity. In another embodiment, the DNA molecule comprise a group II intron sequence that encodes both a group II intron RNA as well as a group II intron encoded protein. The DNA molecule is then expressed in the host cell to provide RNP particles that comprise the group II intron-encoded protein bound to the group II intron RNA. Thereafter, the RNP particles comprising the group II intron-encoded protein and the group II intron RNA are isolated from the cell and treated with a nuclease to remove the RNA and to provide the group II-intron encoded protein. The group II intron-encoded protein is then combined in vitro with the exogenous RNA to provide RNP particles having nucleotide integrase activity.

Methods of making an RNP particle having nucleotide integrase activity

The present invention provides new methods, employing a nucleotide integrase, for cleaving double-stranded and single stranded DNA substrates at specific sites and for attaching nucleic acid molecules to the cleaved DNA substrates. One method uses a nucleotide integrase to cleave one strand of a double-stranded DNA and to concomitantly attach a nucleic acid molecule to the cleaved strand. Another method uses a nucleotide integrase to cleave both strands of a double-stranded DNA substrate and to attach a nucleic acid molecule to one strand of the DNA substrate. Another method uses a nucleotide integrase to cleave both strands of a double-stranded DNA substrate and to attach an RNA molecule to one strand of the substrate and for attaching a cDNA to the other strand of the substrate. Another method cleaves single stranded DNA with the concomitant insertion of a nucleic acid molecule at the cleavage point. The nucleotide integrase comprises an RNP particle which comprises a group II intron RNA bound to a group II intron encoded protein. The present invention also relates to purified and reconstituted RNP particles and reconstituted RNP that cleave DNA substrates.

Method of making an RNA particle for use in cleaving nucleic acid

Ribonucleoprotein particles for cleaving double-stranded DNA and

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Alhambra, CA, United States of America

Huatao Guo