PT  - JOURNAL ARTICLE
AU  - Sophia N. Carrell
AU  - Michael D. O’Connell
AU  - Amy E. Allen
AU  - Stephanie M. Smith
AU  - Gregory T. Reeves
TI  - A Facilitated Diffusion Mechanism Establishes the Drosophila Dorsal Gradient
AID  - 10.1101/057091
DP  - 2016 Jan 01
TA  - bioRxiv
PG  - 057091
4099  - http://biorxiv.org/content/early/2016/06/03/057091.short
4100  - http://biorxiv.org/content/early/2016/06/03/057091.full
AB  - The transcription factor NF-κB plays an important role in the immune system as an apoptotic and inflammatory factor. In the Drosophila melanogaster embryo, a homolog of NF-ΚB called Dorsal (dl) patterns the dorsal-ventral (DV) axis in a concentration-dependent manner. During early development, dl is sequestered outside the nucleus by Cactus (Cact), homologous to IκB. Toll signaling at the ventral midline breaks the dl/Cact complex, allowing dl to enter the nucleus where it transcribes target genes. Here we show that dl accumulates on the ventral side of the embryo over the last 5 cleavage cycles and that this accumulation is the result of facilitated diffusion of dl/Cact complex. We speculate that the predominant role for Cact in DV axis specification is to shuttle dl towards the ventral midline. Given that this mechanism has been found in other, independent systems, we suggest it may be more prevalent than previously thought.