In addition to the core histones, certain HATs acetylate a number of other cellular proteins including transcriptional activators, basal transcription factors, structural proteins, polyamines, and proteins involved in nuclear import. Acetylation of these proteins can alter their ability to interact with their cognate DNA and/or protein substrates. The idea that acetylation can affect protein function in this manner has led to inquiry regarding the role of acetyltransferases in signal transduction pathways and whether an appropriate analogy to kinases and phosphorylation events can be made in this respect.