ADP-ribosylation can affect gene expression at nearly every level of regulation, including chromatin organization, transcription factor recruitment and binding, and mRNA processing.
The organization of nucleosomes is key to regulation of gene expression: the spacing and organization of nucleosomes changes what regions of DNA are available for transcription machinery to bind and transcribe DNA. PARP1, a poly-ADP ribose polymerase, has been shown to affect chromatin structure and promote changes in the organization of nucleosomes through modification of histones.
PARPs have been shown to affect transcription factor structure and cause recruitment of many transcription factors to form complexes at DNA and elicit transcription. Mono(ADP-ribosyl)transferases are also shown to affect transcription factor binding at promoters. For example, PARP14, a mono (ADP-ribosyl)transferase, has been shown to affect STAT transcription factor binding.
Other (ADP-ribosyl)transferases have been shown to modify proteins that bind mRNA, which can cause silencing of that gene transcript.