ZFIN ID: ZDB-PUB-140404-8
TALE factors poise promoters for activation by Hox proteins
Choe, S.K., Ladam, F., and Sagerström, C.G.
Date: 2014
Source: Developmental Cell   28(2): 203-211 (Journal)
Registered Authors: Choe, Seong-Kyu, Sagerström, Charles
Keywords: none
MeSH Terms:
  • Animals
  • Blastula/metabolism
  • Gastrula/metabolism
  • Gene Expression Regulation, Developmental
  • Homeodomain Proteins/genetics
  • Homeodomain Proteins/metabolism*
  • Phosphorylation
  • Positive Transcriptional Elongation Factor B/genetics
  • Positive Transcriptional Elongation Factor B/metabolism
  • Promoter Regions, Genetic*
  • RNA Polymerase II/genetics
  • RNA Polymerase II/metabolism
  • Transcriptional Activation*
  • Zebrafish
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism*
PubMed: 24480644 Full text @ Dev. Cell

Hox proteins form complexes with TALE cofactors from the Pbx and Prep/Meis families to control transcription, but it remains unclear how Hox:TALE complexes function. Examining a Hoxb1b:TALE complex that regulates zebrafish hoxb1a transcription, we find maternally deposited TALE proteins at the hoxb1a promoter already during blastula stages. These TALE factors recruit histone-modifying enzymes to promote an active chromatin profile at the hoxb1a promoter and also recruit RNA polymerase II (RNAPII) and P-TEFb. However, in the presence of TALE factors, RNAPII remains phosphorylated on serine 5 and hoxb1a transcription is inefficient. By gastrula stages, Hoxb1b binds together with TALE factors to the hoxb1a promoter. This triggers P-TEFb-mediated transitioning of RNAPII to the serine 2-phosphorylated form and efficient hoxb1a transcription. We conclude that TALE factors access promoters during early embryogenesis to poise them for activation but that Hox proteins are required to trigger efficient transcription.