Premium
Single molecule transcription factor dynamics in mammalian cells and the syncytial Drosophila embryo
Author(s) -
Darzacq Xavier,
Mir Mustafa
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.255.4
Subject(s) - drosophila embryogenesis , blastoderm , embryo , biology , microbiology and biotechnology , nucleoplasm , morphogen , transcription factor , nuclear transport , biophysics , nucleus , genetics , embryogenesis , cell nucleus , gene , nucleolus
Formation of the large protein complexes regulating transcription such as the pre‐initiation complex (PIC) is the result of equilibrium in between the frequency at which its principal components assemble and disassemble. To date a lot of information has been collected on how the off rate of a specific interaction is regulated. Here I will concentrate on two mechanisms controlling the on rate of proteins assembly at the level of their ability to sample the nucleoplasm using efficient strategies to search for their targets. During early development in the Drosophila embryo, cell fates are determined over the course of just 2 hours with exquisite spatio‐temporal precision. One of the key regulators of this process is the morphogen Bicoid that is enriched at the anterior of the embryo establishing polarity in a concentration dependent manner. Bicoid has also been suspected to play a role in the posterior where there are only a few molecules per nucleus but the lack of a mechanism for such an activation lead to much controversy. Here we use lattice light sheet microscopy to overcome the technical barriers of sample thickness and auto‐fluorescence to characterize the single molecule dynamics of Bicoid. We find that Bicoid binds to DNA transiently consistent with its concentration modulated activity. When analyzing the few molecules present in the posterior nuclei we observed a significant dynamic change affecting the on rates of binding as well as massive clustering of bicoid molecules. In the context of a concentration dependent model for bicoid activity, this data is consistent with a locus dependent and regulated transcriptional function in the drosophila embryo posterior. Different mechanisms of regulation as well as current experiments to sort them apart will be discussed. Support or Funding Information Funding was provided by the National Institute of Health grants (U54‐DK107980) and (U01‐EB021236) to XD. California Institute for Regenerative Medicine (CIRM, LA1‐08013 to XD)