FIG. 6.

Model for regulation of differentiation gene loci in the mammalian gut. Chromatin is represented in green and promoters are represented in pink; the arrow denotes active transcription. Early in intestine development, the abundance of class I HDACs limits histone acetylation at selected differentiation loci. Subsequently, reduced cellular levels of these enzymes favor local chromatin modifications that promote gene transcription. Thus, modification of endogenous class I HDAC levels is likely one of several mechanisms that impose tight temporal control over developmental gene activation.