title: Direct observation of individual endogenous protein complexes in situ by proximity ligation.
abstract: Cellular processes can only be understood as the dynamic interplay of molecules. There is a need for techniques to monitor interactions of endogenous proteins directly in individual cells and tissues to reveal the cellular and molecular architecture and its responses to perturbations. Here we report our adaptation of the recently developed proximity ligation method to examine the subcellular localization of protein-protein interactions at single-molecule resolution. Proximity probes-oligonucleotides attached to antibodies against the two target proteins-guided the formation of circular DNA strands when bound in close proximity. The DNA circles in turn served as templates for localized rolling-circle amplification (RCA), allowing individual interacting pairs of protein molecules to be visualized and counted in human cell lines and clinical specimens. We used this method to show specific regulation of protein-protein interactions between endogenous Myc and Max oncogenic transcription factors in response to interferon-gamma (IFN-gamma) signaling and low-molecular-weight inhibitors.
authors.affiliation: Department of Genetics and Pathology, Rudbeck Laboratory, University of Uppsala, SE-75185 Uppsala, Sweden.
authors.forename: Ola
authors.initials: O
authors.lastname: Söderberg
authors.forename: Mats
authors.initials: M
authors.lastname: Gullberg
authors.forename: Malin
authors.initials: M
authors.lastname: Jarvius
authors.forename: Karin
authors.initials: K
authors.lastname: Ridderstråle
authors.forename: Karl-Johan
authors.initials: KJ
authors.lastname: Leuchowius
authors.forename: Jonas
authors.initials: J
authors.lastname: Jarvius
authors.forename: Kenneth
authors.initials: K
authors.lastname: Wester
authors.forename: Per
authors.initials: P
authors.lastname: Hydbring
authors.forename: Fuad
authors.initials: F
authors.lastname: Bahram
authors.forename: Lars-Gunnar
authors.initials: LG
authors.lastname: Larsson
authors.forename: Ulf
authors.initials: U
authors.lastname: Landegren
mesh_terms: D002468:Cell Physiological Phenomena; D007089:Image Enhancement / Q000379:methods*; D008856:Microscopy, Fluorescence / Q000379:methods*; D025941:Protein Interaction Mapping / Q000379:methods*; D011506:Proteins / Q000378:metabolism*
chemical_list: D011506:Proteins