Desplan et al and Ma et al biochemical analysis
Desplan et al and Dostatni et al transgenic / enhancer analysis
Barkai, Gregor, Holloway models
Notes: Hb reading
Ma Biochemistry Paper (1996)
by DNAse protection assay, less than 4x increase in bcd concentration converts all six sites from unprotected to protected (except A3).
by mobility shift, 4x increase goes from 1 bound (at any of the sites) to 3+ bound.
Hill coefficients by site: A1=5, X1=4, X2=3, X3=3.7, A2=5, A3 = 1.2
Km by site: A1=.75, X1=.75, X2 =.75,X3=1.2,A2=.75,A3=.9
A1 X1 10x higher protection when in natural 41bp separation than when alone. (same at 45 bp separation).
Crosslinking bcd allows detection of dimes, though Gel shift suggest fundamental binding unit is a monomer (which probably interacts directly with its neighbors through a separate region than the DNA binding domain).
Dochi 3x bcd sites restrict hb to the anterior fifth.
Holloway Model: 2 hb sites, 5 bcd sites. hb is made whenever any of the hb sites are bound (at a specific rate k*hb_i, i=1,2) or whenever any of the bcd sites is bound also at site-specific rates.
This is effectively an hb triggered promoter in parallel with a bcd triggered promoter. Binding of hb to the promoter does not reduce the population of bcd bound promoters.