Macromolecular Interactome of Tetrahymena CHD Family Chromatin Remodelers

Tetrahymena thermophila undergoes RNA-guided, DNA elimination during development. Bioinformatic and functional analyses on tChd family chromatin remodelers suggest the proteins are candidate DNA and RNA binding proteins. In vivo and in vitro functional analyses on tChd3 and tChd7 identified diverse macromolecular interactions throughout the lifecycle. Chd3 bound a novel protein named Miz1, which is a candidate E3 SUMO ligase. Chd3 and Miz1 co-localize to vegetatively repressed PDD1, and may regulate transcription via epigenetic SUMOylation of chromatin.

Chd7 binds (un)modified H3K36, and highly transcribed genes during vegetative growth. This binding may regulate transcriptional turnover by Chd7-mediated reading of the acetyl/methyl status at H3K36. In vitro analyses suggest Chd7 binds poly(G) RNAs. G-rich sequences are transcribed during RNA-guided DNA elimination events, and Chd7 may be involved during this part of Tetrahymena development. These analyses provide a glimpse into how RNAs and epigenetics orchestrate chromatin dynamics, in complex eukaryotic regulatory mechanisms.