Fluorescence resonance energy transfer as a rich source of orientational information in nucleic acid structure
Lead Research Organisation:
University of Dundee
Department Name: School of Life Sciences
Abstract
Fluorescence is the most sensitive spectroscopic method used in biological systems, and is widely used to study the structure and dynamics of large biological molecules. Fluorescence resonance energy transfer (FRET) is extensively employed to measure or compare distances in such macromolecules, especially nucleic acids (DNA and RNA). Fluorescence is highly sensitive so that it can be studied at the level of a single molecule and it can be performed inside cells.
FRET results from a coupling between two fluorescent groups attached at known positions in the molecule of interest. This is through space, not requiring physical contact. The efficiency of this process depends upon the distance between the groups, and can be arranged to be in the length range that is optimal for studies of biological molecules. In studies of single molecules this can be used to analyze distances between selected segments of a molecule, and how this changes as a function of time in dynamic processes. Such information is particularly powerful in the study of DNA and RNA structure. However, a well-known complication is that the magnitude of FRET depends on both distance and orientation of the fluorescent groups. If the latter is not properly treated the distance information obtained can be very misleading. This has severely limited obtaining reliable quantitative data from FRET in the past. On the other hand, if the orientation of the fluorescent groups is understood, this can generate reliable distance estimates together with valuable angular information.
Recent work in this laboratory has demonstrated that when certain fluorescent groups (called cyanines) are used in FRET measurements in nucleic acids, they stack onto the ends of double helices where they are oriented in a defined manner. We have used this property to show that we can measure angular information from FRET data, and consequently more reliable distance information. This puts FRET measurements on a reliable quantitative basis and we now wish to develop this as a method to study the structures of DNA and RNA in solution. This should have a major impact in the structural biology and dynamic properties of nucleic acids.
FRET results from a coupling between two fluorescent groups attached at known positions in the molecule of interest. This is through space, not requiring physical contact. The efficiency of this process depends upon the distance between the groups, and can be arranged to be in the length range that is optimal for studies of biological molecules. In studies of single molecules this can be used to analyze distances between selected segments of a molecule, and how this changes as a function of time in dynamic processes. Such information is particularly powerful in the study of DNA and RNA structure. However, a well-known complication is that the magnitude of FRET depends on both distance and orientation of the fluorescent groups. If the latter is not properly treated the distance information obtained can be very misleading. This has severely limited obtaining reliable quantitative data from FRET in the past. On the other hand, if the orientation of the fluorescent groups is understood, this can generate reliable distance estimates together with valuable angular information.
Recent work in this laboratory has demonstrated that when certain fluorescent groups (called cyanines) are used in FRET measurements in nucleic acids, they stack onto the ends of double helices where they are oriented in a defined manner. We have used this property to show that we can measure angular information from FRET data, and consequently more reliable distance information. This puts FRET measurements on a reliable quantitative basis and we now wish to develop this as a method to study the structures of DNA and RNA in solution. This should have a major impact in the structural biology and dynamic properties of nucleic acids.
Planned Impact
The expected outcome of this work will be a methodology for the use of FRET as a structural tool for nucleic acids. This should have a major impact in the structural biology of nucleic acids, and the study of structure and dynamics in single molecules and inside cells. The immediate users are likely to be academic researchers who are studying nucleic acid structure, folding, dynamics and interactions with small molecules and proteins. Thereafter this could become equally useful to researchers in commercial laboratories. FRET-based assays are widely used in many applications, and a greater understanding of the basis of this is likely to prove beneficial. In the course of these studies we hope to perfect a robust approach for the study of the global architecture of folded nucleic acids, their dynamics and their interactions with ligands. We shall make our protocols and computer programs available to other users, principally by downloading from the internet.
Organisations
People |
ORCID iD |
David Lilley (Principal Investigator) |
Publications
Ashraf S
(2017)
Sequence determinants of the folding properties of box C/D kink-turns in RNA.
in RNA (New York, N.Y.)
Ashraf S
(2019)
Effect of methylation of adenine N6 on kink turn structure depends on location.
in RNA biology
Castor D
(2013)
Cooperative control of holliday junction resolution and DNA repair by the SLX1 and MUS81-EME1 nucleases.
in Molecular cell
Daldrop P
(2013)
The plasticity of a structural motif in RNA: structural polymorphism of a kink turn as a function of its environment.
in RNA (New York, N.Y.)
Fessl T
(2013)
Measurement of the change in twist at a helical junction in RNA using the orientation dependence of FRET.
in Biophysical journal
Freeman AD
(2013)
The importance of the N-terminus of T7 endonuclease I in the interaction with DNA junctions.
in Journal of molecular biology
Freeman ADJ
(2014)
GEN1 from a thermophilic fungus is functionally closely similar to non-eukaryotic junction-resolving enzymes.
in Journal of molecular biology
Füchtbauer AF
(2017)
Fluorescent RNA cytosine analogue - an internal probe for detailed structure and dynamics investigations.
in Scientific reports
Harusawa S
(2012)
Synthesis of novel tetrazole C5-linked C0- and C2-ribonucleoside phosphoramidites using MePOM and POM groups for probing RNA catalysis
in Tetrahedron Letters
Description | We have made considerable progress in developing a new approach in fluorescence (optical spectroscopy) that provides angular information in nucleic acid structure. This project is still on-going, but is proceeding very well. For example, we have determined the structure at a three-way helical junction in the RNA of a special element in the hepatitis C virus that allows a ribosome to bind internally and begin protein synthesis. This work continues. |
Exploitation Route | The hepatitis C virus (HCV) infects 170 million people worldwide. Individuals with persistent HCV infection are at significant risk of hepatocellular carcinoma. There is no vaccine, and current therapies are poor. The IRES element could be its 'Achilles heel' and structural work could lead to therapeutic intervention. |
Sectors | Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology |
URL | http://www.dundee.ac.uk/biocentre/nasg/CY/Login.html |
Description | This laboratory performed the first fluorescence resonance energy transfer (FRET) studies in nucleic acids of the modern era. This work has had considerable impact, and our early papers in Nature and PNAS have been cited 358 and 351 times. We also carried out some of the first single-molecule FRET studies of nucleic acids, and our paper in Nature Struc. Biol. has been cited 324 times, and that on ribozyme dynamics in PNAS has been cited 232 times. While most people using FRET have ignored the orientation dependence, we have argued this is important information that should not be neglected. We established the location of cyanine fluorophores on DNA and RNA - our first NMR paper on Cy3 has been cited 266 times. This grant focussed on the orientation dependence (the k^2 parameter) in structural studies on DNA, and our paper in PNAS has been cited 320 times. This approach was applied to the establish the conformation of a three-way RNA junction in the HCV IRES element for example, and to determine the change in helical twist at a junction. We have continued to derive structural information on the location of cyanine fluorophores terminally attached to double-stranded DNA and RNA, and our coordinates have been made freely available for others to use. These studies have established the importance and value of the orientation dependence in fluorescence resonance energy transfer. |
Sector | Education,Pharmaceuticals and Medical Biotechnology |
Title | Cyanine dyes attached to DNA |
Description | The Structure of cyanine fluorophores terminally attached to double-stranded DNA: Implications for FRET studies |
Type Of Material | Database/Collection of data |
Provided To Others? | No |
Impact | Coordinates of our NMR structures of fluorophores attached to dsDNA can be downloaded from this site |
URL | http://www.dundee.ac.uk/biocentre/nasg/CY/cy/CY_main.html |
Title | SAXS analysis of VS ribozyme RNA |
Description | This site provides a description of how to analyze folded RNA structure (here the VS ribozyme) using SAXS. JMOL sessions and movies of the process can be obtained here. |
Type Of Material | Database/Collection of data |
Provided To Others? | No |
Impact | This study was influential, and the methods for transforming bead models into low resolution density maps have become widely used |
URL | http://www.dundee.ac.uk/biocentre/nasg/VS/SAXS_VS/VS_main.html |
Title | The k-turn structure on-line database |
Description | This is an interactive structural database for known k-turn structures in RNA, including both sequence and structural data. For each k-turn the structure can be examined in a J-MOL session, and multiple k-turns compared and superimposed |
Type Of Material | Database/Collection of data |
Year Produced | 2011 |
Provided To Others? | Yes |
Impact | This site regularly gets 10 hits per day |
URL | http://www.dundee.ac.uk/biocentre/nasg/kturn/ |
Description | Aspen Colorado Physics café |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Public/other audiences |
Results and Impact | General public attended talks on biophysics Hopefully people got a better idea of what biophysics is |
Year(s) Of Engagement Activity | 2011 |
Description | Dundee Science Café |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Public/other audiences |
Results and Impact | 80 general public attended lecture on the chemical origins of life Further invitations received |
Year(s) Of Engagement Activity | 2012 |
Description | Fife Science Fare |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Public/other audiences |
Results and Impact | Public lecture on the origins of life Greater understanding and interest in this topic |
Year(s) Of Engagement Activity | 2013 |